Thanks for providing those logs, very helpful.
Of course it is not the Plasma6 desktop crashing the desktop is not starting or it may be something right before the desktop like sddm or systemd or something in the dual graphics setup that is not being handled correctly. Those all remain true for LXQt. In your journal log sddm-helper-start-x11user looks very unhappy.
A first guess: 2 things you could try, they won’t hurt anything:
- Login with Console Mode and run:
sudo systemctl enable sddm.service
If the output shows that command creating a symlink that is likely the problem. If it did create a symlink then reboot and see if system is working properly. If not try:
rpm -e --nodeps sddmand then immediately:
sudo dnf in sddm --refreshreboot and see if that works.
Meanwhile I am posting your logs to developer chat room and we can see if they have any suggestions.
Note: If you want to know more look in the journlctl-b.txt the parts referring to sddm-helper and sddm-helper-start-x11user that part looks pretty abnormal.