drnick1 parent
Another example of this is Left 4 Dead 2, ironically made by Valve. The Windows client is far better, but unfortunately Valve hasn't fixed a bug that prevents joining VAC-secure servers when playing on Proton. This means you need to find an "insecure" server or host your own game.
Civ 5 is another sad example. It has a native port by Aspyr, but it's clearly inferior to getting it to work with proton (and not just for lacking mods).
Same with Civ6, native version has some game breaking bugs but Proton works flawlessly.
Civ7 we don't talk about.