Just after typing my previous comment, gnome-shell did restart in the end, this
is in the log:

Dec 30 23:51:31 nyx kernel: nouveau 0000:23:00.0: Xwayland[5346]: failed to
idle channel 25 [Xwayland[5346]]
Dec 30 23:51:46 nyx kernel: nouveau 0000:23:00.0: Xwayland[5346]: failed to
idle channel 25 [Xwayland[5346]]
Dec 30 23:51:46 nyx kernel: nouveau 0000:23:00.0: fifo: read fault at
0000013000 engine 06 [HOST0] client 07 [GPC0/T1_2] reason 02 [PTE] on channel
25 [00fbf87000 Xwayland[5346]]
Dec 30 23:51:46 nyx kernel: nouveau 0000:23:00.0: fifo: channel 25: killed
Dec 30 23:51:46 nyx kernel: nouveau 0000:23:00.0: fifo: runlist 0: scheduled
for recovery
Dec 30 23:51:46 nyx kernel: nouveau 0000:23:00.0: Xwayland[5346]: channel 25
killed!
Dec 30 23:51:46 nyx kernel: nouveau 0000:23:00.0: Xwayland[5346]:
nv50cal_space: -16
Dec 30 23:51:48 nyx kernel: nouveau 0000:23:00.0: disp: 0x000061ec[0]:
INIT_GENERIC_CONDITON: unknown 0x07
Dec 30 23:52:10 nyx kernel: nouveau 0000:23:00.0: disp: 0x000061ec[0]:
INIT_GENERIC_CONDITON: unknown 0x07

I have a dual display setup (on HiDPI, using fractional scaling), after the
gnome-shell restart the configuration of the displays (how the are arranged,
and which display is primary changed).