PROTON_USE_WINED3D=1 %command%
This one was tricky to makes it work, I'm glad to finally be able to play it without issue after a few years trying
Added I, O and P buttons from keyboard to back buttons to swtich between 2D, 3D and iso views.
While not docuemented, controller is supported, I switched to the gamepad controls. It might be better to just bind the keyboard controls correctly however since the gamepad controls can't be rebound in-game.
Tried with and without esync, no change in performance.
(Reported experimental version: Experimental (Build ID: 7659246))
Tried both 6.19-GE-2 and 6.20-GE-1; would not launch with either. Only launches with Proton Experimental and stable; best performance was on Experimental but was still susceptible to performance drop after some gameplay.
Audio quality drops hand-in-hand with overall performance.
After only a couple minutes performance drops through the floor (massive frame drops, input lag, etc.) whereas it initially plays ok - possible memory issue. Saving the game seems to restore some performance temporarily, but will return to poor performance shortly after.