My keyboard with an accelerator was detected as a joystick controller which resulted in stuck input. I circumvented this by unplugging the keyboard right before launching the game, then replugging it at the main menu. Disabling the joystick detection at the evdev level did not work; it seems Proton / Wine has its own way of detecting raw input devices at a lower level which ignores evdev rules.

Certain maps drop the FPS to just below 30, making it hard to play.

Steam VAC causes multiplayer (incl. single survival w/ AI bots) to crash spontaneously.

VAC