[Linux] No way to get proton games to run whilst also with the overlay

[ThorinWolf]

This thing works for Linux games under Linux quite well - however, not for any Windows games I'm trying to run via Proton. If I try and run direct from the file location, it tries to open it under my system's version of WINE, and fails because there is no version of Steam running on WINE. If I try and use "steam://run/appId" as an arg it just plain launches the game under steam, instead of providing the ability to remote play it. If I try the "workaround" it does the same as the appId method. I've also tried to use a version of GE-Proton to launch the game, with the game as arg, to no avail. Yes, I'm using a donor game (Sonic Mania) and I've locally compiled it. I'm running Arch (the AUR version is no longer maintained) and using steam-native (steam-runtime changes nothing). Any help appreciated.