Also unsure, but adding:

If you installed through Steam, gaming on Linux is pretty seamless and should work out of the box. If you purchased it through another store or acquired through other means, you may have to jump through a hurdle or two to get proton set up and dialed in.

ProtonDB for SE: https://www.protondb.com/app/244850

ProtonDB for SE2: https://www.protondb.com/app/1133870