The game is The Entropy Centre. Midnight Fight Express, which I have finished right before, doesn’t seem to be affected.

Since 2 days ago the game (not Steam) started returning the error:

"A D3D11-compatible GPU (Feature Level 11.0, Shader Model 5.0) is required to run the engine."

I am on LMDE6.

Proton Hotfix or Experimental or 9.0-4 are not working.

Proton 8.0-5 is the first one that works, but with some significant lagging, but I am positive I played the same version of the game using Experimental a few days ago with no lagging and on same Nvidia drivers (535.216.01).

An FPS counter titled VK (I guess from Vulkan) shows when running 8.0, while it didn’t in Experimental.

I have tried resetting the shader precaching in the settings, but nothing changes.

The game was also uninstalled and reinstalled, to no avail.

Any tips for debugging this?