Mostly I can only describe it as “game no worky”. Steam pretends to launch a game, then nothing happens. My hypothesis is that Steam does something to the runtime environment that fucks with some games.

One other thing that I’ve noticed is that on Wine/Proton environments launched from Steam, the lettered drives (aside from C:) are mounted as some kind of overlay filesystem. Writing to them (e.g. by an installer) causes data to be written into memory, not to the mass storage where the drive targets are located.