Thankfully that has been improving [1] and non-kernel is 100% possible today [2] with valve has so much on documentation and support for game and anti cheat developers to accomplish this.
Unfortunately many of these developers believe that kernel-level is mandatory (by virtue of believing that it actually works to prevent _all_ cheating, which we know it doesn't).
[1]: https://www.gamingonlinux.com/anticheat/ [2]: https://partner.steamgames.com/doc/steamdeck/proton