This is kinda on the game developer. There are anti-cheat systems which work fine on Steam Deck already, as long as the developer checks the box to allow it (as I understand it, it is just about that simple for EAC, one of the bigger anti-cheat options). But if the dev doesn't care, or actively doesn't want to support Linux like in the case of Epic, then Valve can't really patch around that.
Sadly, there is a fundamental incompatibility between successful anti-cheat systems and Linux, mainly that the user is fully in charge of their computer. Anti-cheats work by ensuring certain modifications aren’t made to the system the game is running on, and this relies on the operating system being trusted by the anti-cheat software. With Linux, a user is in full control and can just tell the kernel to lie to the anti-cheat system, completely bypassing it. In windows, there are things the user is not in control of and the anti cheat can be sure are correct.
Until anti cheat design changes entirely (and it may not be fully possible), the freedom and control Linux provides simply doesn’t work with them.
They could conceivably just restrict it to certain kernels and checksum stuff couldn’t they? Like restrict it to the last three Ubuntu LTS releases and the last N updates of the mainline kernel?
What I don’t know about this is a lot, so I will admit I am speaking out of my ass here.
Sure, but those specific kernels would require some sort of verification method to make sure they are actually the kernel it says it is (and not a modified version pretending to not be modified) which would require code signing by a trusted third pasty, use of Trusted Platform Modules, and restrictions on what modifications a user can make to their kernel.
All of these things are pretty much non-starters for Linux users. You might as well just use windows if you are going to go that route.
