SteamOS has a "desktop mode" even on the Steam Deck, so no you don't have to worry about being locked into a ten-foot UI like a smart TV to do non-gaming tasks.
Worth noting that KDE OS (whoops nope it's called KDE Linux), which is currently in development, is also basically going to be SteamOS in all but name: Arch-based, immutable (meaning the entire OS is treated as a single "package" that gets updates maybe once a month like Windows instead of each component updating whenever it wants), and of course using KDE for its desktop environment. So if you have the patience to wait for that, it should be ready for prime time within the year.