Yeah, I think the original iteration of SteamOS was based on Debian/Ubuntu but the current release is based on Arch Linux. I tinkered with SteamOS in a VM when it came out and it was very clunky but I imagine they have fixed a lot since then.
The only thing I use Windows for is if a game doesn't work well under Linux. It's a over glorified gaming system now. Especially with all of the work done in Proton, Windows is hardly ever needed and I don't play any of the "AAA" titles since they all went woke and gay so I don't care about playing them on "release" or right after a patch that could break stuff.