> This list also overlooks other very popular games that aren’t on Steam

Well yes, it is, as the title makes pretty clear, the top 50 games on Steam. That said, non-Steam games can work just fine with Proton, wrappers like Lutris make this only a couple clicks more than Steam.

Fortnite is limited by EAC: https://lutris.net/games/fortnite/, and I'm not very familiar with Warzone but I suspect it's a similar situation.

Non native multiplayer games are quite often a no go, which was my gripe with putting GTA V on the list since the concurrent player base is nearly all due to GTAO and if you run it on Linux through proton you risk a ban.