Step 1: Use proton, not linux beta branch
Step 2: Launch with -force-opengl option
??????
PROFIT

With OpenGL forced, it works better than translating API calls from DX11 to Vulkan
I tried to force this game to use Vulkan too, but it crashes as soon as it needs to render anything (2d menu will work on higher framerate, though)
You could probably find this info on ProtonDB, but I'll leave it here