The problem is not that anyone can modify the Steam Deck, after all it can be done with any Windows based system as well. Most and the biggest cheat program and programs are running on Windows. I don’t think giving up Linux as it is is a good thing and follow footsteps of Windows by incorporating more DRM, more controls, more hardware and software restrictions, just to make sure a deep Kernel level access of a rootkit based anti cheat tool can run.

The focus should be a different on: Make Steam Deck more popular as a target for publishers (meaning a big audience) and make it as easy as possible for developers (Proton does a good job). The problem isn’t a technical problem to solve in my opinion, so no need to make it “worse”. And Valve maintaining two different operating system versions, splitting up the user AND developer eco system, to test for isn’t good solution either. Suddenly people have to track not only if a game runs on Steam Deck, but also explain them on top of Proton and all other stuff that they need an alternate version. The website for the games would need to list both compatibility too. It’s a mess.

I understand your intention and why this is suggested by you. I just don’t think its healthy and would not even guarantee to solve the issues at all. The devs and publisher still would need to cooperate and support it officially. I don’t think any online game with anti cheat that runs on Steam Deck has a problem with cheaters using Linux. They have a problem with cheaters using Windows, even with the most intensive rootkit anti cheat installed and running at all times (Vanguard). I would not approve your suggestion (note I did not downvote, because you just want to discuss this).