Proton has become astonishingly good.
Even niche titles either work, or at worst I need to use a specific build of Proton (usually Proton GE for some obscure video formats).
I also have had good luck using Bottles to run Battle.net for Diablo 3 and 4.
I don’t play many competitive multiplayer games though, where very aggressive anti-cheat can be a problem.
The primary games that don’t work (yet) are Genshin Impact and Honkai Star Rail, both by HoYo. There’s some particular quirk of their anti-cheat that causes the games to crash instantly. That said, it’s worth noting that occasionally Genshin Impact has worked for a few weeks, so HoYo seems to be testing a change that might allow it to work consistently eventually.
You have to agree to it in order to view YouTube. If the software doesn’t present those terms, it in itself is in violation.