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.

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.

I use KUbuntu. It's got the packages of Ubuntu, but seems somehow to be better across the board.

Unlike with Reddit, this was already clearly and obviously against terms of service.

IIRC, you can make an alternative front end to YouTube, but it has to include the video ads. Somewhat ironically, many of those aren't even from YouTube themselves, but especially on videos with music, they're assigned by the RIAA to cover licensing costs.

If Reddit had done what YouTube does and just added a requirement for apps to display the sponsored posts, there would certainly be some mildly annoyed users, but it would not have come to the current level.