I honestly don't know why so many people say that anti-cheat with Proton or SteamMachines won't work. SteamOS is an immutable Linux - especially with their own SteamMachine they can enable SecureBoot and attestation that you are using the SteamOS verbatim efi boot file, kernel, and corret system fs image - all signed by Valve. Just as Battlefield 6 does on windows (relying on SecureBoot). That would still allow you to install other OSes on your SteamDeck/SteamMachine, but it would fail the anticheat attestation. I personally see the push in hardware from Valve particular so that they can support anti-cheat on linux.