Fedora Silverblue.

Or really any immutable OS; they would have to go way out of their way to even edit system files, much less break the system. I just recommend Silverblue because gnome is really hard for an inexperienced user to break.

Bazzite and Chimera are “SteamOS-like” distros that are more focused on providing a game console like experience.

They’re immutable operating systems, and the primary UI is Steam. Definitely usable as a desktop PC but that isn’t really their target niche.