Back in March on 5.11, people were having luck with GTK based greeters but Qt based ones weren't working (e.g. SDDM). So Googling around the error that @jayache80 reported, I found some references to people having weird problems with Qt that were fixed with setting QT_X11_NO_MITSHM=1 in someplace like /etc/environment. Maybe this explains why some people have luck and some don't? I'll admit that this is far-fetched, but it might be worth a shot given that it is low effort to try. The rabbit hole I went down are in the links below. Disabling the nvidia splash screen with Option "NoLogo" "1" in xorg.conf might not help, but it wouldn't hurt either.
https://forum.mxlinux.org/viewtopic.php?t=53653
https://forum.mxlinux.org/viewtopic.php?f=108&t=53603&start=10
Pinned Comments
JerryXiao commented on 2022-10-13 03:51 (UTC) (edited on 2022-10-14 02:44 (UTC) by JerryXiao)
For testing users, contributors: check out https://github.com/archlinux-jerry/nvidia-340xx
Warning: force push may happen to match the aur tree