Valve has recognized this is a threat to the success of the Steam Deck and helped Proton support at least two prominent anti-cheat tools (EAC and BattlEye). But it remains to be seen if we'll see widespread acceptance from developers. Fortnite in particular has come out that they won't enable it. Free-to-play games have a more sensitive threat perception.

On the site, you can review games that are known to use anti-cheat here: https://www.protondb.com/explore?selectedFilters=antiCheat

And to clarify, I'm not a dev on any of the underlying Proton technologies. I just run a community site for it.