@TPO100Cofficial
Example:
/home/abaddon/.steam/steam/steamapps/common/Proton 6.3/dist/bin/(wine or wine64) <path_to_your_install.exe>
Though, to be fare there might be better ways such as through Lutris or PlayOnLinux and specifying the Steam Wine paths in there and using their UIs to do the magic.
I mean installing, not running it, because SFM isn't, IIRC, in the user's library. (that, or i made horrible mistakes,) making it so I'm not able to set it to install with Steam Play tools.
Source Filmmaker should be in your Steam Library as something that's available to everybody, however, it's categorically Software instead of Games. In the Steam library view, you may need to select Software in the dropdown list under the Home button in the upper left corner, or search for Source Filmmaker. After that the options to tell Steam to use Proton should be the same as any other game.
proton 6.3x1 2021-04