You want SteamTinkerLaunch, which the Git page mentions there's another program I can't recall the name of right now (proton something) you can use to install it.
If you're on a Debian based OS the version of YAD you can get is laughably out of date (0.4 vs the minimum 7.0) so you'll have to compile that yourself but that's ezpz
With STL enabled and set as your comparability tool launch it and install MO2 and mod away to your heart's content
I used Vortex instead because I hate everyone else and like watching them cringe when I say that. 0 issues.
Oh, proton will need to be ABOVE 8.5c to work with certain mods. 9.0 works great ime