Finally ~/.config/QtProject.conf is not the cause of my problem.
Today the problem come back …
I make a strace of nemo launch
newfstatat(AT_FDCWD, "/var/lib/snapd/desktop/pixmaps", 0x7ffca9c74080, 0) = -1 ENOENT (Aucun fichier ou dossier de ce nom)
newfstatat(AT_FDCWD, "/usr/share/nemo/icons", {st_mode=S_IFDIR|0755, st_size=4096, ...}, 0) = 0
newfstatat(AT_FDCWD, "/usr/share/nemo/icons", {st_mode=S_IFDIR|0755, st_size=4096, ...}, 0) = 0
openat(AT_FDCWD, "/usr/share/nemo/icons/icon-theme.cache", O_RDONLY) = -1 ENOENT (Aucun fichier ou dossier de ce nom)
openat(AT_FDCWD, "/usr/share/nemo/icons", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 12
fstat(12, {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
getdents64(12, 0x587823a29c20 /* 3 entries */, 32768) = 80
getdents64(12, 0x587823a29c20 /* 0 entries */, 32768) = 0
close(12) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
eventfd2(0, EFD_CLOEXEC|EFD_NONBLOCK) = 12
write(7, "\1\0\0\0\0\0\0\0", 8) = 8
futex(0x5878237e1ac0, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0x5878237e1800, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0x5878237dbba8, FUTEX_WAKE_PRIVATE, 1) = 1
poll([{fd=12, events=POLLIN}], 1, 25000) = 1 ([{fd=12, revents=POLLIN}])
read(12, "\1\0\0\0\0\0\0\0", 8) = 8
write(7, "\1\0\0\0\0\0\0\0", 8) = 8
futex(0x5878237e1ac0, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0x5878237e1800, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0x5878237dbba8, FUTEX_WAKE_PRIVATE, 1) = 1
poll([{fd=12, events=POLLIN}], 1, 25000) = 1 ([{fd=12, revents=POLLIN}])
read(12, "\1\0\0\0\0\0\0\0", 8) = 8
write(12, "\1\0\0\0\0\0\0\0", 8) = 8
futex(0x5878239eddf0, FUTEX_WAKE_PRIVATE, 2147483647) = 0
close(12) = 0
eventfd2(0, EFD_CLOEXEC|EFD_NONBLOCK) = 12
write(7, "\1\0\0\0\0\0\0\0", 8) = 8
futex(0x5878237e1ac0, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0x5878237e1800, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0x5878237dbba8, FUTEX_WAKE_PRIVATE, 1) = 1
poll([{fd=12, events=POLLIN}], 1, 25000) = 0 (Timeout) <---------------------------------- This event take 25 sec
write(12, "\1\0\0\0\0\0\0\0", 8) = 8
futex(0x587823aa99a0, FUTEX_WAKE_PRIVATE, 2147483647) = 0
close(12) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x5878237d3620, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0x7e054c6bdf78, FUTEX_WAIT_PRIVATE, 1, NULL) = 0
futex(0x5878237d38b0, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7e054c6bdff8, FUTEX_WAKE_PRIVATE, 2147483647) = 0