I just ran an Online-Update on one of my OES2018SP2 servers. This contained the update "SUSE-SLE-SERVER-12-SP5-2020-2388 - Recommended update for Mesa" which changes mesa from 18.3.2-14.3.2 to 18.3.2-14.6.1 .
After applying this update the local graphical console is broken. The nice error in the gdm log.x is
LLVM ERROR: inconsistency in registered CommandLine options
which does not help at all in finding the culprit. I than inspected the updates for changes to the X server environment and found the mesa-update.
Reinstalling the old version for all updated mesa-components and restarting xdm got the graphical console back.