For me, since I use the flatpak version of steam, at no point have I ever provided the admin password in order to install steam or any game. It, like all of my desktop software, runs in it's own little sandbox that has limited access to the rest of the computer. It would take a somewhat sophisticated attack for an anticheat to actually run in kernalspace on the host os.

But that's also why companies like riot have their anticheat block Linux from running the game at all.

If Linux becomes a populate enough platform, I'm sure cheaters will start using it to get around anticheat and something else will have to be done. Until then, I'm happy knowing this is a problem that I can mostly avoid.