Akonadi does not start

I have a problem with akonadi, it does not start and also starting it manually does not work :-/

n3150% akonadictl restart
Akonadi is not running.
n3150% akonadictl start  
org.kde.pim.akonadictl: Starting Akonadi Server...
org.kde.pim.akonadictl:    done.
n3150% Connecting to deprecated signal QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString)
org.kde.pim.akonadiserver: Starting up the Akonadi Server...
akonadi.collectionattributetable                   OK
akonadi.collectionmimetyperelation                 OK
akonadi.collectionpimitemrelation                  OK
akonadi.collectiontable                            OK
akonadi.flagtable                                  OK
akonadi.mimetypetable                              OK
akonadi.parttable                                  OK
akonadi.parttypetable                              OK
akonadi.pimitemflagrelation                        OK
akonadi.pimitemtable                               OK
akonadi.pimitemtagrelation                         OK
akonadi.relationtable                              OK
/usr/bin/mysqlcheck: Got error: 2013: Lost connection to server during query when executing 'CHECK TABLE ...  FOR UPGRADE'
org.kde.pim.akonadiserver: Failed to verify database server version
org.kde.pim.akonadiserver: Query error: "Server has gone away QMYSQL: Unable to execute query"
org.kde.pim.akonadiserver: Database error: ""
org.kde.pim.akonadiserver: Shutting down AkonadiServer...
org.kde.pim.akonadicontrol: Application '/usr/bin/akonadiserver' exited normally...

n3150% akonadictl start
org.kde.pim.akonadictl: Starting Akonadi Server...
org.kde.pim.akonadictl:    done.
n3150% Connecting to deprecated signal QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString)
org.kde.pim.akonadiserver: Starting up the Akonadi Server...
akonadi.collectionattributetable                   OK
akonadi.collectionmimetyperelation                 OK
akonadi.collectionpimitemrelation                  OK
akonadi.collectiontable                            OK
akonadi.flagtable                                  OK
akonadi.mimetypetable                              OK
akonadi.parttable                                  OK
akonadi.parttypetable                              OK
akonadi.pimitemflagrelation                        OK
akonadi.pimitemtable                               OK
akonadi.pimitemtagrelation                         OK
akonadi.relationtable                              OK
akonadi.relationtypetable                          OK
akonadi.resourcetable                              OK
akonadi.schemaversiontable                         OK
akonadi.tagattributetable                          OK
akonadi.tagremoteidresourcerelationtable           OK
akonadi.tagtable                                   OK
akonadi.tagtypetable                               OK
org.kde.pim.akonadiserver: Running DB initializer
org.kde.pim.akonadiserver: "\nSql error: Server has gone away QMYSQL: Unable to execute query\nQuery: CREATE TABLE PimItemFlagRelation (PimItem_id BIGINT NOT NULL, Flag_id BIGINT NOT NULL, PRIMARY KEY (PimItem_id, Flag_id), FOREIGN KEY (PimItem_id) REFERENCES PimItemTable(id) ON UPDATE CASCADE ON DELETE CASCADE, FOREIGN KEY (Flag_id) REFERENCES FlagTable(id) ON UPDATE CASCADE ON DELETE CASCADE)  COLLATE=utf8_general_ci DEFAULT CHARSET=utf8"
org.kde.pim.akonadiserver: Unable to initialize database.
QMYSQLResult::cleanup: unable to free statement handle
QMYSQLResult::cleanup: unable to free statement handle
QMYSQLResult::cleanup: unable to free statement handle
QMYSQLResult::cleanup: unable to free statement handle
QMYSQLResult::cleanup: unable to free statement handle
org.kde.pim.akonadiserver: Shutting down AkonadiServer...
org.kde.pim.akonadicontrol: Application '/usr/bin/akonadiserver' exited normally...

Digging further with journalctl shows that mariadb coredumps:

Apr 20 21:03:14 n3150 systemd-coredump[1066]: Process 991 (akonadiserver) of user 2809 dumped core.
                                              
                                              Module linux-vdso.so.1 with build-id 145557cd9a22cb461959707f99e8eea14c339a8e
                                              Module libmariadb.so.3 with build-id a8417a59d92d04878a77d20a0f33979a346b3d48
                                              Module libqsqlmysql.so with build-id 432cf29189c0519226b3dd5bec1e8d43b6376457
                                              Module libbrotlicommon.so.1 with build-id a4ba3f4b4571c8272343b621da812a6e24a202a7
                                              Module libbrotlidec.so.1 with build-id 45defc036e918e0140a72f1fbce6e7692d38241d
                                              Module libbz2.so.1.0 with build-id 919597c477c9b2cb9cdbb7745ed6494ac0e6da60
                                              Module libgpg-error.so.0 with build-id 82524ee3d1c4c2244d7cfdcc1e6eea5f9855f6c6
                                              Module libgraphite2.so.3 with build-id 47761dc11e553f519cde97ed9ee985be12ccdae2
                                              Module libfreetype.so.6 with build-id 2c4fc9c3e3c6324e6a495e760c2b9b62559d695c
                                              Module libGLX.so.0 with build-id 2a08836c6e6126ce9ff4496b6aacaf29ae9b4e7b
                                              Module libGLdispatch.so.0 with build-id 501765b3a78d668860fa54229b18107473aeda4c
                                              Module libXdmcp.so.6 with build-id 8ca0792d23c8b8b4c0864297512349292bea5955
                                              Module libXau.so.6 with build-id 1c67764663e07bec24d8951e5fd93f4d165979ff
                                              Module libpcre.so.1 with build-id 845483dd0acba86de9f0313102bebbaf3ce52767
                                              Module libicudata.so.70 with build-id e1dcc2a88cfaafed882d09c90c668af0eed4efed
                                              Module libgcrypt.so.20 with build-id 8bf3cb884124273640de797a3e77d86c98434ea4
                                              Module libcap.so.2 with build-id eb6dae97527fc89dbb0d5bb581a15acd02ae9f56
                                              Module liblz4.so.1 with build-id e63600ab23b2f6997f42fac2fa56e1f02ce159a1
                                              Module libresolv.so.2 with build-id 46ffdf3d477a170314060c26927470d7399bc900
                                              Module libkeyutils.so.1 with build-id ac405ddd17be10ce538da3211415ee50c8f8df79
                                              Module libdl.so.2 with build-id bb9bd2657bfba9f60bd34d2050cc63a7eb024bc4
                                              Module libkrb5support.so.0 with build-id adf65240a4d2aba772d7a0772b4d015469934113
                                              Module libcom_err.so.2 with build-id 358b783c9b3d12ba8248519ea2e7f3da4c4e0297
                                              Module libk5crypto.so.3 with build-id eb8220b8f36675aac769450be4cb6bb7f97ec38a
                                              Module libkrb5.so.3 with build-id 72d26767c5cb1097db75a5f5bff88860233c902b
                                              Module libpthread.so.0 with build-id 7fa8b52fae071a370ba4ca32bf9490a30aff31c4
                                              Module libmd4c.so.0 with build-id 2151dba72cdc9960097e6e960a58a2f03c8bb96e
                                              Module libharfbuzz.so.0 with build-id ac8220c9649822c84097ad58e80b97a86f3b4f7f
                                              Module libpng16.so.16 with build-id 2dc0bce07f199bf983c07a05fb95a6f4af83a9b3
                                              Module libGL.so.1 with build-id 912ac4f37a9fa2d5abcf7a9088c9983cfe46f12a
                                              Module libQt5Widgets.so.5 with build-id 243a6a0410a5ef13a0a1917e20947ceb54bac1ea
                                              Module libxcb-keysyms.so.1 with build-id 333e5eb4075795f947c924a2085f17e2e2ae7147
                                              Module libxcb.so.1 with build-id 0d1ef11740a5daad2ee331e812a51aa6574af222
                                              Module ld-linux-x86-64.so.2 with build-id c09c6f50f6bcec73c64a0b4be77eadb8f7202410
                                              Module libglib-2.0.so.0 with build-id d6c7c03d71a1b71f59e10016323136de55f43266
                                              Module libzstd.so.1 with build-id 3bccb8fe08e48d5ea135b1d0f99de0d771dd752f
                                              Module libpcre2-16.so.0 with build-id 195fbccafbcff538ce13805ba687514fb614c5ed
                                              Module libicuuc.so.70 with build-id 2e245c2bf12f95fd8ab79b3a4be99524677cbd70
                                              Module libicui18n.so.70 with build-id 95af755fca990df26753a7d720b8e3ae24270e42
                                              Module libdouble-conversion.so.3 with build-id d162eb67b00f523a3f146b1077ae00fe04d5fb85
                                              Module libsystemd.so.0 with build-id 05d0460efefd339d315812f9506aecc5a5d22200
                                              Module libdbus-1.so.3 with build-id 7f4b16b4b407cbae2d7118d6f99610e29a18a56a
                                              Module libcrypto.so.1.1 with build-id f94a24f9ce8f3f394c3df23f7d436796797d4459
                                              Module libssl.so.1.1 with build-id 54f796076979dc9b6ff9ac3c39e250db86652924
                                              Module libgssapi_krb5.so.2 with build-id e6e098ad51ce7bdd3dbe902d7b0f69a90f8a9e08
                                              Module libz.so.1 with build-id 1fb800ce60ddb605ebe23f9702adcd341c7c8970
                                              Module liblzma.so.5 with build-id 8b615460aa230708c5183f16bede67aa0437d95e
                                              Module libm.so.6 with build-id 596b63a006a4386dcab30912d2b54a7a61827b07
                                              Module libQt5Gui.so.5 with build-id 542bfee317d9c0b49a210bf6751eb05fa0e0229b
                                              Module libQt5X11Extras.so.5 with build-id 25320ee0d79d41ea309fc03b608da2d35d24e6b6
                                              Module libX11.so.6 with build-id 1bf9c2f1c9e2f823a1200b41ffa6b09943edf886
                                              Module libKF5WindowSystem.so.5 with build-id 126371f20fe6ec8475d4a55feff2612062f0f7c6
                                              Module libc.so.6 with build-id 85766e9d8458b16e9c7ce6e07c712c02b8471dbc
                                              Module libgcc_s.so.1 with build-id 5d817452a709ca3a213341555ddcf446ecee37fa
                                              Module libstdc++.so.6 with build-id 88ad4eff81a00c684abfe0f863e87434123d8943
                                              Module libQt5Core.so.5 with build-id 0212696a875fc5c74cfd3f91671ebc3c2311b34c
                                              Module libQt5Xml.so.5 with build-id c117dde732dd4946c4842e65b3beb75ad290cf82
                                              Module libQt5DBus.so.5 with build-id eaadac7eb0682c8accdb8431fb928470c0546840
                                              Module libQt5Sql.so.5 with build-id 03b37a8f06cec32dfbcb264dc0a2ec2c9f15b0b4
                                              Module libQt5Network.so.5 with build-id 0267597d5dced5fa6a6f6bb100c2e8ef5106611d
                                              Module libKF5AkonadiPrivate.so.5 with build-id ab457f83cda63f490365b0d825fffb2972f04354
                                              Module libKF5CoreAddons.so.5 with build-id 11187221bb1fa2ebd85562beb177f190663bf9a6
                                              Module libKF5Crash.so.5 with build-id da12fe66a78b772a0aeaf3fea2d3aae4e1aa40b1
                                              Module akonadiserver with build-id 44e9722ddaa263f2c856fb5e9ceb1e8f64bf13cd
                                              Stack trace of thread 991:
                                              #0  0x00007f4d8089334c __pthread_kill_implementation (libc.so.6 + 0x8f34c)
                                              #1  0x00007f4d808464b8 raise (libc.so.6 + 0x424b8)
                                              #2  0x00007f4d80830534 abort (libc.so.6 + 0x2c534)
                                              #3  0x00007f4d80ac27ee _ZN9__gnu_cxx27__verbose_terminate_handlerEv (libstdc++.so.6 + 0x997ee)
                                              #4  0x00007f4d80acec4c _ZN10__cxxabiv111__terminateEPFvvE (libstdc++.so.6 + 0xa5c4c)
                                              #5  0x00007f4d80acecb9 _ZSt9terminatev (libstdc++.so.6 + 0xa5cb9)
                                              #6  0x00007f4d80acef5e __cxa_throw (libstdc++.so.6 + 0xa5f5e)
                                              #7  0x000055d3affeda73 n/a (akonadiserver + 0x30a73)
                                              #8  0x000055d3b0091fc0 n/a (akonadiserver + 0xd4fc0)
                                              #9  0x000055d3b0075f06 n/a (akonadiserver + 0xb8f06)
                                              #10 0x000055d3affffbf7 n/a (akonadiserver + 0x42bf7)
                                              #11 0x000055d3b0001b48 n/a (akonadiserver + 0x44b48)
                                              #12 0x00007f4d80eff7d6 _ZN7QObject5eventEP6QEvent (libQt5Core.so.5 + 0x2b07d6)
                                              #13 0x00007f4d80edb58e _ZN16QCoreApplication15notifyInternal2EP7QObjectP6QEvent (libQt5Core.so.5 + 0x28c58e)
                                              #14 0x00007f4d80edc0a9 _ZN23QCoreApplicationPrivate16sendPostedEventsEP7QObjectiP11QThreadData (libQt5Core.so.5 + 0x28d0a9)
                                              #15 0x00007f4d80f23678 n/a (libQt5Core.so.5 + 0x2d4678)
                                              #16 0x00007f4d7f279163 g_main_context_dispatch (libglib-2.0.so.0 + 0x55163)
                                              #17 0x00007f4d7f2cf9e9 n/a (libglib-2.0.so.0 + 0xab9e9)
                                              #18 0x00007f4d7f2766c5 g_main_context_iteration (libglib-2.0.so.0 + 0x526c5)
                                              #19 0x00007f4d80f2757a _ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE (libQt5Core.so.5 + 0x2d857a)
                                              #20 0x00007f4d80ed388b _ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE (libQt5Core.so.5 + 0x28488b)
                                              #21 0x00007f4d80edefd7 _ZN16QCoreApplication4execEv (libQt5Core.so.5 + 0x28ffd7)
                                              #22 0x000055d3afffacc5 n/a (akonadiserver + 0x3dcc5)
                                              #23 0x00007f4d80831310 __libc_start_call_main (libc.so.6 + 0x2d310)
                                              #24 0x00007f4d808313c1 __libc_start_main@@GLIBC_2.34 (libc.so.6 + 0x2d3c1)
                                              #25 0x000055d3afffdbe5 n/a (akonadiserver + 0x40be5)
                                              
                                              Stack trace of thread 998:
                                              #0  0x00007f4d8090a2af __poll (libc.so.6 + 0x1062af)
                                              #1  0x00007f4d7f2cf976 n/a (libglib-2.0.so.0 + 0xab976)
                                              #2  0x00007f4d7f2766c5 g_main_context_iteration (libglib-2.0.so.0 + 0x526c5)
                                              #3  0x00007f4d80f2757a _ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE (libQt5Core.so.5 + 0x2d857a)
                                              #4  0x00007f4d80ed388b _ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE (libQt5Core.so.5 + 0x28488b)
                                              #5  0x00007f4d80d36a56 _ZN7QThread4execEv (libQt5Core.so.5 + 0xe7a56)
                                              #6  0x00007f4d811d93a9 n/a (libQt5DBus.so.5 + 0x233a9)
                                              #7  0x00007f4d80d338cc n/a (libQt5Core.so.5 + 0xe48cc)
                                              #8  0x00007f4d808915c2 start_thread (libc.so.6 + 0x8d5c2)
                                              #9  0x00007f4d80916584 __clone (libc.so.6 + 0x112584)
                                              ELF object binary architecture: AMD x86-64
Apr 20 21:03:14 n3150 akonadi_control[877]: org.kde.pim.akonadicontrol: ProcessControl: Application "/usr/bin/akonadiserver" stopped unexpectedly ( "Process crashed" )

If this was after an update, did you completely reboot the system?
Maybe try this

and starting kmail or an akonadictl start does not solve the problem unfortunately.

Apr 21 19:57:08 n3150 systemd-coredump[5202]: Process 5177 (mysqld) of user 2809 dumped core.
                                             
                                             Module linux-vdso.so.1 with build-id 145557cd9a22cb461959707f99e8eea14c339a8e
                                             Module libgpg-error.so.0 with build-id 82524ee3d1c4c2244d7cfdcc1e6eea5f9855f6c6
                                             Module libpthread.so.0 with build-id 7fa8b52fae071a370ba4ca32bf9490a30aff31c4
                                             Module libgcrypt.so.20 with build-id 8bf3cb884124273640de797a3e77d86c98434ea4
                                             Module libcap.so.2 with build-id eb6dae97527fc89dbb0d5bb581a15acd02ae9f56
                                             Module liblz4.so.1 with build-id e63600ab23b2f6997f42fac2fa56e1f02ce159a1
                                             Module libzstd.so.1 with build-id 3bccb8fe08e48d5ea135b1d0f99de0d771dd752f
                                             Module liblzma.so.5 with build-id 8b615460aa230708c5183f16bede67aa0437d95e
                                             Module ld-linux-x86-64.so.2 with build-id c09c6f50f6bcec73c64a0b4be77eadb8f7202410
                                             Module libc.so.6 with build-id 85766e9d8458b16e9c7ce6e07c712c02b8471dbc
                                             Module libgcc_s.so.1 with build-id 5d817452a709ca3a213341555ddcf446ecee37fa
                                             Module libm.so.6 with build-id 596b63a006a4386dcab30912d2b54a7a61827b07
                                             Module libstdc++.so.6 with build-id 88ad4eff81a00c684abfe0f863e87434123d8943
                                             Module libz.so.1 with build-id 1fb800ce60ddb605ebe23f9702adcd341c7c8970
                                             Module libsystemd.so.0 with build-id 05d0460efefd339d315812f9506aecc5a5d22200
                                             Module libaio.so.1 with build-id 695ade37b71ebaed9669c51cdb05c0e25d8a9a0d
                                             Module libcrypto.so.1.1 with build-id f94a24f9ce8f3f394c3df23f7d436796797d4459
                                             Module libssl.so.1.1 with build-id 54f796076979dc9b6ff9ac3c39e250db86652924
                                             Module libcrypt.so.2 with build-id a0a45f81771945f0559d04e93726d245159930da
                                             Module mariadbd with build-id c125e9ad8ecfabeaee53f8eaecf92cf7bc2d9a11
                                             Stack trace of thread 5177:
                                             #0  0x00007fdcf29202af __poll (libc.so.6 + 0x1062af)
                                             #1  0x000055953dd5cae3 _Z26handle_connections_socketsv (mariadbd + 0x641ae3)
                                             #2  0x000055953dd68d44 _Z11mysqld_mainiPPc (mariadbd + 0x64dd44)
                                             #3  0x00007fdcf2847310 __libc_start_call_main (libc.so.6 + 0x2d310)
                                             #4  0x00007fdcf28473c1 __libc_start_main@@GLIBC_2.34 (libc.so.6 + 0x2d3c1)
                                             #5  0x000055953dd20005 _start (mariadbd + 0x605005)
                                             
                                             Stack trace of thread 5178:
                                             #0  0x00007fdcf28a415a __futex_abstimed_wait_common (libc.so.6 + 0x8a15a)
                                             #1  0x00007fdcf28a6c64 pthread_cond_timedwait@@GLIBC_2.3.2 (libc.so.6 + 0x8cc64)
                                             #2  0x000055953e54ebf8 n/a (mariadbd + 0xe33bf8)
                                             #3  0x00007fdcf28a75c2 start_thread (libc.so.6 + 0x8d5c2)
                                             #4  0x00007fdcf292c584 __clone (libc.so.6 + 0x112584)
                                             
                                             Stack trace of thread 5188:
                                             #0  0x00007fdcf285d24a __sigtimedwait (libc.so.6 + 0x4324a)
                                             #1  0x000055953dd54e1c signal_hand (mariadbd + 0x639e1c)
                                             #2  0x000055953e2ff323 n/a (mariadbd + 0xbe4323)
                                             #3  0x00007fdcf28a75c2 start_thread (libc.so.6 + 0x8d5c2)
                                             #4  0x00007fdcf292c584 __clone (libc.so.6 + 0x112584)
                                             
                                             Stack trace of thread 5179:
                                             #0  0x00007fdcf28a415a __futex_abstimed_wait_common (libc.so.6 + 0x8a15a)
                                             #1  0x00007fdcf28a6c64 pthread_cond_timedwait@@GLIBC_2.3.2 (libc.so.6 + 0x8cc64)
                                             #2  0x000055953e28aa89 n/a (mariadbd + 0xb6fa89)
                                             #3  0x000055953e292d3a n/a (mariadbd + 0xb77d3a)
                                             #4  0x00007fdcf28a75c2 start_thread (libc.so.6 + 0x8d5c2)
                                             #5  0x00007fdcf292c584 __clone (libc.so.6 + 0x112584)
                                             
                                             Stack trace of thread 5181:
                                             #0  0x00007fdcf28a415a __futex_abstimed_wait_common (libc.so.6 + 0x8a15a)
                                             #1  0x00007fdcf28a6c64 pthread_cond_timedwait@@GLIBC_2.3.2 (libc.so.6 + 0x8cc64)
                                             #2  0x000055953e490ea2 n/a (mariadbd + 0xd75ea2)
                                             #3  0x00007fdcf2bfc4d4 execute_native_thread_routine (libstdc++.so.6 + 0xd54d4)
                                             #4  0x00007fdcf28a75c2 start_thread (libc.so.6 + 0x8d5c2)
                                             #5  0x00007fdcf292c584 __clone (libc.so.6 + 0x112584)
                                             
                                             Stack trace of thread 5180:
                                             #0  0x00007fdcf2925a9d syscall (libc.so.6 + 0x10ba9d)
                                             #1  0x000055953e4eefe6 _ZN5tpool9aio_linux23getevent_thread_routineEPS0_ (mariadbd + 0xdd3fe6)
                                             #2  0x00007fdcf2bfc4d4 execute_native_thread_routine (libstdc++.so.6 + 0xd54d4)
                                             #3  0x00007fdcf28a75c2 start_thread (libc.so.6 + 0x8d5c2)
                                             #4  0x00007fdcf292c584 __clone (libc.so.6 + 0x112584)
                                             
                                             Stack trace of thread 5184:
                                             #0  0x00007fdcf28a415a __futex_abstimed_wait_common (libc.so.6 + 0x8a15a)
                                             #1  0x00007fdcf28a6f32 pthread_cond_clockwait@GLIBC_2.30 (libc.so.6 + 0x8cf32)
                                             #2  0x000055953e4f22df _ZN5tpool19thread_pool_generic14wait_for_tasksERSt11unique_lockISt5mutexEPNS_11worker_dataE (mariadbd + 0xdd72df)
                                             #3  0x000055953e4f2501 _ZN5tpool19thread_pool_generic8get_taskEPNS_11worker_dataEPPNS_4taskE (mariadbd + 0xdd7501)
                                             #4  0x000055953e4f359f _ZN5tpool19thread_pool_generic11worker_mainEPNS_11worker_dataE (mariadbd + 0xdd859f)
                                             #5  0x00007fdcf2bfc4d4 execute_native_thread_routine (libstdc++.so.6 + 0xd54d4)
                                             #6  0x00007fdcf28a75c2 start_thread (libc.so.6 + 0x8d5c2)
                                             #7  0x00007fdcf292c584 __clone (libc.so.6 + 0x112584)
                                             
                                             Stack trace of thread 5183:
                                             #0  0x00007fdcf28a934c __pthread_kill_implementation (libc.so.6 + 0x8f34c)
                                             #1  0x00007fdcf285c4b8 raise (libc.so.6 + 0x424b8)
                                             #2  0x00007fdcf28465c6 abort (libc.so.6 + 0x2c5c6)
                                             #3  0x000055953dcbdce8 n/a (mariadbd + 0x5a2ce8)
                                             #4  0x000055953dc99059 n/a (mariadbd + 0x57e059)
                                             #5  0x000055953dcb6e6e n/a (mariadbd + 0x59be6e)
                                             #6  0x000055953e452565 n/a (mariadbd + 0xd37565)
                                             #7  0x000055953e442340 n/a (mariadbd + 0xd27340)
                                             #8  0x000055953e4f33aa _ZN5tpool10task_group7executeEPNS_4taskE (mariadbd + 0xdd83aa)
                                             #9  0x000055953e4f35d0 _ZN5tpool19thread_pool_generic11worker_mainEPNS_11worker_dataE (mariadbd + 0xdd85d0)
                                             #10 0x00007fdcf2bfc4d4 execute_native_thread_routine (libstdc++.so.6 + 0xd54d4)
                                             #11 0x00007fdcf28a75c2 start_thread (libc.so.6 + 0x8d5c2)
                                             #12 0x00007fdcf292c584 __clone (libc.so.6 + 0x112584)
                                             
                                             Stack trace of thread 5189:
                                             #0  0x00007fdcf28a415a __futex_abstimed_wait_common (libc.so.6 + 0x8a15a)
                                             #1  0x00007fdcf28a6960 pthread_cond_wait@@GLIBC_2.3.2 (libc.so.6 + 0x8c960)
                                             #2  0x000055953de6d839 handle_manager (mariadbd + 0x752839)
                                             #3  0x000055953e2ff323 n/a (mariadbd + 0xbe4323)
                                             #4  0x00007fdcf28a75c2 start_thread (libc.so.6 + 0x8d5c2)
                                             #5  0x00007fdcf292c584 __clone (libc.so.6 + 0x112584)
                                             
                                             Stack trace of thread 5182:
                                             #0  0x00007fdcf2925a9d syscall (libc.so.6 + 0x10ba9d)
                                             #1  0x00007fdcf2e46221 io_submit (libaio.so.1 + 0x1221)
                                             #2  0x000055953e4ef210 n/a (mariadbd + 0xdd4210)
                                             #3  0x000055953e3dfe8a n/a (mariadbd + 0xcc4e8a)
                                             #4  0x000055953e4bc179 n/a (mariadbd + 0xda1179)
                                             #5  0x000055953e4a0aba n/a (mariadbd + 0xd85aba)
                                             #6  0x000055953e4a18eb n/a (mariadbd + 0xd868eb)
                                             #7  0x000055953e48db1c n/a (mariadbd + 0xd72b1c)
                                             #8  0x000055953e48e20d n/a (mariadbd + 0xd7320d)
                                             #9  0x000055953e4f35e2 _ZN5tpool19thread_pool_generic11worker_mainEPNS_11worker_dataE (mariadbd + 0xdd85e2)
                                             #10 0x00007fdcf2bfc4d4 execute_native_thread_routine (libstdc++.so.6 + 0xd54d4)
                                             #11 0x00007fdcf28a75c2 start_thread (libc.so.6 + 0x8d5c2)
                                             #12 0x00007fdcf292c584 __clone (libc.so.6 + 0x112584)
                                             
                                             Stack trace of thread 5197:
                                             #0  0x00007fdcf28a415a __futex_abstimed_wait_common (libc.so.6 + 0x8a15a)
                                             #1  0x00007fdcf28a6c64 pthread_cond_timedwait@@GLIBC_2.3.2 (libc.so.6 + 0x8cc64)
                                             #2  0x000055953dfcb4d3 _Z24do_handle_one_connectionP7CONNECTb (mariadbd + 0x8b04d3)
                                             #3  0x000055953dfcb992 handle_one_connection (mariadbd + 0x8b0992)
                                             #4  0x000055953e2ff323 n/a (mariadbd + 0xbe4323)
                                             #5  0x00007fdcf28a75c2 start_thread (libc.so.6 + 0x8d5c2)
                                             #6  0x00007fdcf292c584 __clone (libc.so.6 + 0x112584)
                                             
                                             Stack trace of thread 5195:
                                             #0  0x00007fdcf292e3ce __send (libc.so.6 + 0x1143ce)
                                             #1  0x000055953e236e32 vio_write (mariadbd + 0xb1be32)
                                             #2  0x000055953e21280b net_real_write (mariadbd + 0xaf780b)
                                             #3  0x000055953dd9c8e1 _ZN8Protocol12net_send_eofEP3THDjj (mariadbd + 0x6818e1)
                                             #4  0x000055953dd90f46 _ZN8Protocol13end_statementEv (mariadbd + 0x675f46)
                                             #5  0x000055953de7fdcb _Z16dispatch_command19enum_server_commandP3THDPcjb (mariadbd + 0x764dcb)
                                             #6  0x000055953de82b29 _Z10do_commandP3THDb (mariadbd + 0x767b29)
                                             #7  0x000055953dfcb474 _Z24do_handle_one_connectionP7CONNECTb (mariadbd + 0x8b0474)
                                             #8  0x000055953dfcb992 handle_one_connection (mariadbd + 0x8b0992)
                                             #9  0x000055953e2ff323 n/a (mariadbd + 0xbe4323)
                                             #10 0x00007fdcf28a75c2 start_thread (libc.so.6 + 0x8d5c2)
                                             #11 0x00007fdcf292c584 __clone (libc.so.6 + 0x112584)
                                             
                                             Stack trace of thread 5193:
                                             #0  0x00007fdcf28a415a __futex_abstimed_wait_common (libc.so.6 + 0x8a15a)
                                             #1  0x00007fdcf28a6f32 pthread_cond_clockwait@GLIBC_2.30 (libc.so.6 + 0x8cf32)
                                             #2  0x000055953e4f22df _ZN5tpool19thread_pool_generic14wait_for_tasksERSt11unique_lockISt5mutexEPNS_11worker_dataE (mariadbd + 0xdd72df)
                                             #3  0x000055953e4f2501 _ZN5tpool19thread_pool_generic8get_taskEPNS_11worker_dataEPPNS_4taskE (mariadbd + 0xdd7501)
                                             #4  0x000055953e4f359f _ZN5tpool19thread_pool_generic11worker_mainEPNS_11worker_dataE (mariadbd + 0xdd859f)
                                             #5  0x00007fdcf2bfc4d4 execute_native_thread_routine (libstdc++.so.6 + 0xd54d4)
                                             #6  0x00007fdcf28a75c2 start_thread (libc.so.6 + 0x8d5c2)
                                             #7  0x00007fdcf292c584 __clone (libc.so.6 + 0x112584)
                                             
                                             Stack trace of thread 5192:
                                             #0  0x00007fdcf28a415a __futex_abstimed_wait_common (libc.so.6 + 0x8a15a)
                                             #1  0x00007fdcf28a6f32 pthread_cond_clockwait@GLIBC_2.30 (libc.so.6 + 0x8cf32)
                                             #2  0x000055953e4f22df _ZN5tpool19thread_pool_generic14wait_for_tasksERSt11unique_lockISt5mutexEPNS_11worker_dataE (mariadbd + 0xdd72df)
                                             #3  0x000055953e4f2501 _ZN5tpool19thread_pool_generic8get_taskEPNS_11worker_dataEPPNS_4taskE (mariadbd + 0xdd7501)
                                             #4  0x000055953e4f359f _ZN5tpool19thread_pool_generic11worker_mainEPNS_11worker_dataE (mariadbd + 0xdd859f)
                                             #5  0x00007fdcf2bfc4d4 execute_native_thread_routine (libstdc++.so.6 + 0xd54d4)
                                             #6  0x00007fdcf28a75c2 start_thread (libc.so.6 + 0x8d5c2)
                                             #7  0x00007fdcf292c584 __clone (libc.so.6 + 0x112584)
                                             
                                             Stack trace of thread 5191:
                                             #0  0x00007fdcf28a415a __futex_abstimed_wait_common (libc.so.6 + 0x8a15a)
                                             #1  0x00007fdcf28a6f32 pthread_cond_clockwait@GLIBC_2.30 (libc.so.6 + 0x8cf32)
                                             #2  0x000055953e4f22df _ZN5tpool19thread_pool_generic14wait_for_tasksERSt11unique_lockISt5mutexEPNS_11worker_dataE (mariadbd + 0xdd72df)
                                             #3  0x000055953e4f2501 _ZN5tpool19thread_pool_generic8get_taskEPNS_11worker_dataEPPNS_4taskE (mariadbd + 0xdd7501)
                                             #4  0x000055953e4f359f _ZN5tpool19thread_pool_generic11worker_mainEPNS_11worker_dataE (mariadbd + 0xdd859f)
                                             #5  0x00007fdcf2bfc4d4 execute_native_thread_routine (libstdc++.so.6 + 0xd54d4)
                                             #6  0x00007fdcf28a75c2 start_thread (libc.so.6 + 0x8d5c2)
                                             #7  0x00007fdcf292c584 __clone (libc.so.6 + 0x112584)
                                             
                                             Stack trace of thread 5185:
                                             #0  0x00007fdcf28a415a __futex_abstimed_wait_common (libc.so.6 + 0x8a15a)
                                             #1  0x00007fdcf28a6f32 pthread_cond_clockwait@GLIBC_2.30 (libc.so.6 + 0x8cf32)
                                             #2  0x000055953e4f22df _ZN5tpool19thread_pool_generic14wait_for_tasksERSt11unique_lockISt5mutexEPNS_11worker_dataE (mariadbd + 0xdd72df)
                                             #3  0x000055953e4f2501 _ZN5tpool19thread_pool_generic8get_taskEPNS_11worker_dataEPPNS_4taskE (mariadbd + 0xdd7501)
                                             #4  0x000055953e4f359f _ZN5tpool19thread_pool_generic11worker_mainEPNS_11worker_dataE (mariadbd + 0xdd859f)
                                             #5  0x00007fdcf2bfc4d4 execute_native_thread_routine (libstdc++.so.6 + 0xd54d4)
                                             #6  0x00007fdcf28a75c2 start_thread (libc.so.6 + 0x8d5c2)
                                             #7  0x00007fdcf292c584 __clone (libc.so.6 + 0x112584)
                                             
                                             Stack trace of thread 5190:
                                             #0  0x00007fdcf28a415a __futex_abstimed_wait_common (libc.so.6 + 0x8a15a)
                                             #1  0x00007fdcf28a6f32 pthread_cond_clockwait@GLIBC_2.30 (libc.so.6 + 0x8cf32)
                                             #2  0x000055953e4f22df _ZN5tpool19thread_pool_generic14wait_for_tasksERSt11unique_lockISt5mutexEPNS_11worker_dataE (mariadbd + 0xdd72df)
                                             #3  0x000055953e4f2501 _ZN5tpool19thread_pool_generic8get_taskEPNS_11worker_dataEPPNS_4taskE (mariadbd + 0xdd7501)
                                             #4  0x000055953e4f359f _ZN5tpool19thread_pool_generic11worker_mainEPNS_11worker_dataE (mariadbd + 0xdd859f)
                                             #5  0x00007fdcf2bfc4d4 execute_native_thread_routine (libstdc++.so.6 + 0xd54d4)
                                             #6  0x00007fdcf28a75c2 start_thread (libc.so.6 + 0x8d5c2)
                                             #7  0x00007fdcf292c584 __clone (libc.so.6 + 0x112584)
                                             
                                             Stack trace of thread 5186:
                                             #0  0x00007fdcf28a415a __futex_abstimed_wait_common (libc.so.6 + 0x8a15a)
                                             #1  0x00007fdcf28a6f32 pthread_cond_clockwait@GLIBC_2.30 (libc.so.6 + 0x8cf32)
                                             #2  0x000055953e4f22df _ZN5tpool19thread_pool_generic14wait_for_tasksERSt11unique_lockISt5mutexEPNS_11worker_dataE (mariadbd + 0xdd72df)
                                             #3  0x000055953e4f2501 _ZN5tpool19thread_pool_generic8get_taskEPNS_11worker_dataEPPNS_4taskE (mariadbd + 0xdd7501)
                                             #4  0x000055953e4f359f _ZN5tpool19thread_pool_generic11worker_mainEPNS_11worker_dataE (mariadbd + 0xdd859f)
                                             #5  0x00007fdcf2bfc4d4 execute_native_thread_routine (libstdc++.so.6 + 0xd54d4)
                                             #6  0x00007fdcf28a75c2 start_thread (libc.so.6 + 0x8d5c2)
                                             #7  0x00007fdcf292c584 __clone (libc.so.6 + 0x112584)
                                             ELF object binary architecture: AMD x86-64
Apr 21 19:57:09 n3150 systemd[1]: systemd-coredump@1-5201-0.service: Deactivated successfully.
Apr 21 19:57:09 n3150 kernel: audit: type=1131 audit(1650563829.034:148): pid=1 uid=0 auid=4294967295 ses=4294967295 subj==unconfined msg='unit=systemd-coredump@1-5201-0 comm="systemd" exe="/usr/lib/systemd/systemd" hostname=? addr=? terminal=? res=success'
Apr 21 19:57:09 n3150 audit[1]: SERVICE_STOP pid=1 uid=0 auid=4294967295 ses=4294967295 subj==unconfined msg='unit=systemd-coredump@1-5201-0 comm="systemd" exe="/usr/lib/systemd/systemd" hostname=? addr=? terminal=? res=success'
Apr 21 19:57:09 n3150 systemd[1]: systemd-coredump@1-5201-0.service: Consumed 2.193s CPU time.
Apr 21 19:57:09 n3150 akonadiserver[5168]: org.kde.pim.akonadiserver: "\nSql error: Server has gone away QMYSQL: Unable to execute query\nQuery: ALTER TABLE TagAttributeTable ADD COLUMN id BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY"
Apr 21 19:57:09 n3150 akonadiserver[5168]: org.kde.pim.akonadiserver: Unable to initialize database.

You can also try this:

akonadictl stop
#rename akonadi directory (or delete it if you have the balls)
mv /home/username/.local/share/akonadi /home/username/.local/share/akonadi_backup
#start akonadi
akonadictl start

That makes akonadi start, all messages need to be downloaded again from the IMAP Server, but the kmail configuration is at least preserved. If this is a good way to clear the akonadi cache, I learnt something.

Thank you.

n3150% akonadictl stop
Akonadi is not running.
n3150% mv ~/.local/share/akonadi ~/.local/share/akonadi_backup
n3150% akonadictl start 
org.kde.pim.akonadictl: Starting Akonadi Server...
org.kde.pim.akonadictl:    done.
n3150% Connecting to deprecated signal QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString)
org.kde.pim.akonadiserver: Starting up the Akonadi Server...
Installing MariaDB/MySQL system tables in '/home/rd/.local/share/akonadi/db_data/' ...
OK

To start mysqld at boot time you have to copy
support-files/mysql.server to the right place for your system


Two all-privilege accounts were created.
One is root@localhost, it has no password, but you need to
be system 'root' user to connect. Use, for example, sudo mysql
The second is rd@localhost, it has no password either, but
you need to be the system 'rd' user to connect.
After connecting you can set the password, if you would need to be
able to connect as any of these users with a password and without sudo

See the MariaDB Knowledgebase at https://mariadb.com/kb

You can start the MariaDB daemon with:
cd '/usr' ; /usr/bin/mysqld_safe --datadir='/home/rd/.local/share/akonadi/db_data/'

You can test the MariaDB daemon with mysql-test-run.pl
cd '/usr/mysql-test' ; perl mysql-test-run.pl

Please report any problems at https://mariadb.org/jira

The latest information about MariaDB is available at https://mariadb.org/.

Consider joining MariaDB's strong and vibrant community:
https://mariadb.org/get-involved/

/usr/bin/mysqlcheck: Got error: 1049: Unknown database 'akonadi' when selecting the database
org.kde.pim.akonadiserver: Running DB initializer
org.kde.pim.akonadiserver: DB initializer done
Connecting to deprecated signal QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString)
org.kde.pim.akonadicontrol: Akonadi server is now operational.
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f2064005590) )
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f2064005590) identified as "ETMCalendarMonitor - 94227464571376"
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f20640300e0) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f2064056d50) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f2064057060) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f20640606a0) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f2064069b80) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f20640730b0) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f206407c5d0) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f2064085940) )
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f20640300e0) identified as "AgentBaseChangeRecorder - 94813820738880"
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f2064085940) identified as "akonadi_birthdays_resource - 94813820747200"
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f20640a92b0) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f20640b3230) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f20640b3540) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f20640bc800) )
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f2064056d50) identified as "AgentBaseChangeRecorder - 94650319464960"
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f20640d7600) )
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f2064057060) identified as "AgentBaseChangeRecorder - 93936893233456"
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f20640606a0) identified as "AgentBaseChangeRecorder - 93853796962400"
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f2064069b80) identified as "AgentBaseChangeRecorder - 94138048171632"
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f20640730b0) identified as "AgentBaseChangeRecorder - 94197270349696"
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f20641047c0) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f206410d4a0) )
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f206407c5d0) identified as "AgentBaseChangeRecorder - 94214297324224"
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f20640a92b0) identified as "AgentBaseChangeRecorder - 94492509272816"
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f20640b3540) identified as "AgentBaseChangeRecorder - 94287956579808"
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f20640b3230) identified as "AgentBaseChangeRecorder - 94022777612624"
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f20641047c0) identified as "akonadi_maildispatcher_agent - 94022777628448"
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f206410d4a0) identified as "SpecialCollectionsMonitor - 94022777629216"
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f20640bc800) identified as "AgentBaseChangeRecorder - 93995711931088"
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f2064151320) )
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f20640d7600) identified as "AgentBaseChangeRecorder - 94101683865904"
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f206415b1e0) )
org.kde.pim.akonadiserver: Subscriber "" disconnected
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f206416ce00) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f206416ce00) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f206417a840) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f2064176610) )
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f2064151320) identified as "AgentBaseChangeRecorder - 94682863212320"
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f206416ce00) identified as "Archive Mail Kernel ETM - 94682863375488"
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f206417a840) identified as "ArchiveMailCollectionMonitor - 94682863378624"
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f2064179ad0) )
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f206415b1e0) identified as "AgentBaseChangeRecorder - 94680922061296"
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f20641ab910) )
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f2064176610) identified as "AgentBaseChangeRecorder - 94238634027216"
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f20641ab910) identified as "UnifiedMailboxChangeRecorder - 140721005897056"
org.kde.pim.akonadiserver: Subscriber "" disconnected
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f20641ce560) )
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f20641ce560) )
org.kde.pim.akonadiserver: Handler exception when handling command FetchItems on connection akonadi_unifiedmailbox_agent (0x55e23231d480) : Dude, WTF?!?
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f20641d78e0) )
org.kde.pim.akonadiserver: Handler exception when handling command FetchItems on connection akonadi_unifiedmailbox_agent (0x55e23231d480) : Dude, WTF?!?
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f20641d8930) )
org.kde.pim.akonadiserver: Handler exception when handling command FetchItems on connection akonadi_unifiedmailbox_agent (0x55e23231d480) : Dude, WTF?!?
org.kde.pim.akonadiserver: Handler exception when handling command FetchItems on connection akonadi_unifiedmailbox_agent (0x55e23231d480) : Dude, WTF?!?
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f2064179ad0) identified as "AgentBaseChangeRecorder - 94238373203856"
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f20641ce560) identified as "MailFilter Kernel ETM - 94238373367184"
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f20641d78e0) identified as "MailFilterCollectionMonitor - 94238373369536"
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f20641d8930) identified as "MailFilterItemMonitor - 139850376318144"
org.kde.pim.akonadiserver: New notification connection (registered as Akonadi::Server::NotificationSubscriber(0x7f20641db590) )
org.kde.pim.akonadiserver: Subscriber Akonadi::Server::NotificationSubscriber(0x7f20641db590) identified as "SpecialCollectionsMonitor - 94238373473120"

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