Oops sorry I missed this until now. I'll maybe have a look at it again after the next update is done, but fixing it would probably require a big re-write of a lot of the game, so unfortunately I wouldn't bet on it. I think if you just add it as a non-steam game on Steam (in Library, click "Games" at the top and then "Add a Non-Steam Game to My Library"), and enable proton (right click the game, click Properties, click Compatibility and choose Proton) that should work? (although I haven't tested this myself so it's possible that doesn't work)