Unable to start SDDM greeter after update

After the last update of testing branch, I’m unable to log in the system with SDDM greeter.

The output of journalctl --boot=0 is

giu 30 17:31:07 thinkpad sddm-helper[2564]: [PAM] Starting...
giu 30 17:31:07 thinkpad sddm-helper[2564]: [PAM] Authenticating...
giu 30 17:31:07 thinkpad sddm-helper[2564]: [PAM] returning.
giu 30 17:31:07 thinkpad sddm-helper[2564]: pam_unix(sddm-greeter:session): session opened for user sddm(uid=969) by (uid=0)
giu 30 17:31:07 thinkpad sddm-helper[2564]: pam_systemd(sddm-greeter:session): New sd-bus connection (system-bus-pam-systemd-2564) opened.
giu 30 17:31:07 thinkpad systemd-logind[1022]: New session c1 of user sddm.
giu 30 17:31:07 thinkpad systemd[1]: Created slice User Slice of UID 969.
giu 30 17:31:07 thinkpad systemd[1]: Starting User Runtime Directory /run/user/969...
giu 30 17:31:07 thinkpad systemd[1]: Finished User Runtime Directory /run/user/969.
giu 30 17:31:07 thinkpad systemd[1]: Starting User Manager for UID 969...
giu 30 17:31:07 thinkpad unix_chkpwd[2568]: could not obtain user info (sddm)
giu 30 17:31:07 thinkpad (systemd)[2567]: PAM failed: Authentication service cannot retrieve authentication info
giu 30 17:31:07 thinkpad (systemd)[2567]: user@969.service: Failed to set up PAM session: Operation not permitted
giu 30 17:31:07 thinkpad (systemd)[2567]: user@969.service: Failed at step PAM spawning /usr/lib/systemd/systemd: Operation not permitted
giu 30 17:31:07 thinkpad systemd[1]: user@969.service: Main process exited, code=exited, status=224/PAM
giu 30 17:31:07 thinkpad systemd[1]: user@969.service: Failed with result 'exit-code'.
giu 30 17:31:07 thinkpad systemd[1]: Failed to start User Manager for UID 969.
giu 30 17:31:07 thinkpad systemd[1]: Dependency failed for Session c1 of User sddm.
giu 30 17:31:07 thinkpad systemd[1]: session-c1.scope: Job session-c1.scope/start failed with result 'dependency'.
giu 30 17:31:07 thinkpad sddm-helper[2564]: pam_systemd(sddm-greeter:session): Failed to create session: Job 2845 for unit 'session-c1.scope' failed with 'dependency'
giu 30 17:31:07 thinkpad sddm-helper[2564]: Starting X11 session: "/usr/bin/X -dpi 114 -background none -seat seat0 -noreset -keeptty -novtswitch -verbose 3" "/usr/bin/sddm-greeter-qt6 --socket /tmp/sddm--ZEfpoe >
giu 30 17:31:07 thinkpad sddm-helper[2570]: Jumping to VT 1
giu 30 17:31:07 thinkpad sddm-helper[2570]: VT mode fixed
giu 30 17:31:07 thinkpad sddm[1216]: Greeter session started successfully
giu 30 17:31:07 thinkpad sddm-helper-start-x11user[2570]: QDir::mkpath: Empty or null file name
giu 30 17:31:07 thinkpad sddm-helper-start-x11user[2570]: Failed to create xauth file
giu 30 17:31:07 thinkpad systemd-coredump[2571]: Process 2570 (sddm-helper-sta) of user 969 terminated abnormally with signal 6/ABRT, processing...
giu 30 17:31:07 thinkpad systemd[1]: Started Process Core Dump (PID 2571/UID 0).
giu 30 17:31:08 thinkpad systemd-coredump[2574]: [🡕] Process 2570 (sddm-helper-sta) of user 969 dumped core.

                                                 Stack trace of thread 2570:
                                                 #0  0x00007f5e9bea8e44 n/a (libc.so.6 + 0x94e44)
                                                 #1  0x00007f5e9be50a30 raise (libc.so.6 + 0x3ca30)
                                                 #2  0x00007f5e9be384c3 abort (libc.so.6 + 0x244c3)
                                                 #3  0x00007f5e9c48c6b7 n/a (libQt6Core.so.6 + 0x8c6b7)
                                                 #4  0x00007f5e9c48ce5b _ZNK14QMessageLogger5fatalEPKcz (libQt6Core.so.6 + 0x8ce5b)
                                                 #5  0x0000585feff31636 n/a (sddm-helper-start-x11user + 0x7636)
                                                 #6  0x0000585feff35ce4 n/a (sddm-helper-start-x11user + 0xbce4)
                                                 #7  0x00007f5e9be39c88 n/a (libc.so.6 + 0x25c88)
                                                 #8  0x00007f5e9be39d4c __libc_start_main (libc.so.6 + 0x25d4c)
                                                 #9  0x0000585feff37565 n/a (sddm-helper-start-x11user + 0xd565)
                                                 ELF object binary architecture: AMD x86-64
giu 30 17:31:08 thinkpad sddm-helper[2564]: [PAM] Closing session

I can start the system if autologin is enabled in sddm.conf but if I log out to change user sddm greeter dumps.