Summary of "Anti Cheat at Embark Studios" prensentation by Embark Studios Senior Software Engineer Tom van Dijck, at devcom in Germany on August 24.

... Linux presents an even worse situation. Because users can custom-build the OS kernel, embedding a cheat directly into the kernel and compiling it makes it nearly impossible for a game to detect its existence. "How do you detect that?" van Dijck asked, adding that while support for SteamOS and Proton will remain, platform requirements will become stricter.

Though he mentions anti-cheat on Linux being more challenging to implement that on Windows, he doesn't seem to think that it's impossible. He goes on to talk about "undetectable" cheating hardware becoming cheaper, which sounds like a bigger problem, but he sounds optimistic about being able to detect those as well.

IMO "platform requirements will become stricter" could mean something like only allowing signed kernels with anti-cheat module built in + secure boot.