gdm3 stopped working after hardware update

[mrmazda]

IME, Xorg.0.log (or Xorg.[0-9].log[.old]) is traditionally found in /var/log/, and/or in more recent releases of Gnome and various other DEs in ~/.local/share/xorg/. I'm not sure whether Wayland sessions produce anything elsewhere than in the journal.

[_VZ]

I'd recommend that the OP try and grab the X11 and waylaid startup log files which usefully reside at /var/logs/X11 and /var/log/wayland.

Thanks for your reply, but:

1. There are no Wayland logs to speak of and, anyhow, Wayland works fine. The only problem is that gdm3 doesn't launch it gdm-wayland-session in the first place.
2. X logs seem fine too, but I'm not really interested in debugging X problems, as I don't want to use X anyhow.

I'm using the machine just fine by logging on the console and launch sway manually, so the real problem is that I hate not understanding how things work and I still have absolutely no idea why does gdm3 decide to run gdm-x-session here, instead of gdm-wayland-session. When I have enough free time I'm going to recompile it from source and try debugging it, but this might have to wait for a while...

[_VZ]

Just to close this discussion, I've finally found the answer and it has nothing to do with hardware update, sorry for the red herring

The real problem is that I had installed DEB package from https://www.nomachine.com/ for testing and even though I have quickly uninstalled it because it doesn't work at all under Wayland, I didn't realize just how broken their package was: one of the (many wrong) things it does is to insert a reference to /usr/NX/scripts/env/nxpreload.sh into /usr/lib/systemd/user/org.gnome.Shell@wayland.service and uninstalled NX package does not remove this from there, explaining why this service couldn't be started any more. Just removing it from there allows gdm to launch Wayland session normally.

Sorry for wasting everyone's time, retrospectively it's clear that the original question was completely impossible to answer.