Technically, steamOS because it’s designed to play games and it’s what the steam deck uses. That probably won’t have many other non-gaming features though, and I’ve personally never used it. In my experience, you can get most games without a hyper-aggressive anti cheat working on any Linux distro with varying degrees of effort, just a matter of having all the needed libraries installed! The more popular distros like Ubuntu, popOS, Fedora, even Arch (btw) should have a lot of helpful information out there on how to get Lutris or Steam set up.