Hi, I've got the same problem, also on Arch, same graphics card. As far as I can determine, it's an error in the last few AMDGPU drivers.
So far I've found two workarounds:
- Set engine flag -shadow_quality 2. AMDGPU can handle the lower quality.
- Use AMDGPU-PRO's OpenGL library. It results in lower FPS, but is stable even with -shadow_quality 4
To do that, I've built but did not install amdgpu-pro-libgl from aur, uncompressed it to get a .pkg folder,
put that into /opt/fs2_open, and edited the knossos.desktop file to set the following envvars:
Exec=env QT_QPA_PLATFORM= LD_LIBRARY_PATH="/opt/fs2_open/amdgpu-pro-libgl-20.40_1147286-1-x86_64.pkg/opt/amdgpu-pro/lib/x86_64-linux-gnu:${LD_LIBRARY_PATH}" LIBGL_DRIVERS_PATH="/opt/fs2_open/amdgpu-pro-libgl-20.40_1147286-1-x86_64.pkg/usr/lib/x86_64-linux-gnu/dri/" dri_driver="amdgpu" python3 -mknossos %U
You'll need to edit the path depending on which version of AMDGPU-PRO you're building.
This way, your other applications still use the AMDGPU driver, and you can still use gnome-wayland, for example.
I've also thought of trying out OpenGL drivers from older mesa versions this way, but as of yet I have no experience with that approach.
EDIT: I was a little unclear here. With AMDGPU I meant the open-source graphics stack (Kernel module amdgpu + mesa's OpenGL RadeonSI) as opposed to AMDGPU-PRO stack (Kernel module amdgpu + AMD's OpenGL AMDGPU-PRO). The error seems to be in radeonsi.