I think by forum rules your issue should require a new topic.
However, let’s not clutter the support section with Linux-related stuff.
libGL error: failed to create dri screen
libGL error: failed to load driver: nouveau
DXVK is attempting to load the open source NVIDIA driver nouveau, which I assume is already suppressed by the proprietary nvidia module it should be using instead, given you loaded into singleplayer and probably run other games on your machine.
Try reinstalling the official NVIDIA driver and check the module status with:
lsmod | grep -i nvidia
lsmod | grep -i nouveau
If by any chance you have an integrated GPU, I’m afraid it’s correlated with this.
Try all approaches in the fashion of DRI_PRIME=1 that enforce the use of your dGPU.
Yes, both the Lutris and Proton Wine forks get stuck at file integrity checks.
I think the issue will be gone before the platform is playable for non-development purposes.
Other than that, everything runs flawless on ProtonGE even without shared resources support, too bad for the anticheat being disabled.