I wanted to do use SteamOS for our LR PC, our kitchen ambiance PC and our MBR PC but instead installed Ubuntu (upgraded to Kubuntu) then disabled Snap because SteamOS which runs KDE and was a great call by Valve, is built on Arch, a bad call IMHO.
I'd be curious to hear why. Arch deserves it's reputation for poor stability, but for Valve's application with OSTree and immutable root should work fine. For users who don't want to tinker, they can receive a quality first-party experience with smooth upgrades. Users that do want to tinker are largely funneled into using Flatpak or AppImage, which are much more stable than AUR packages.
Never had any issues with updating or using it, but it's because I have set up everything myself and never touched AUR. Still nuked it favor on FreeBSD and then NixOS eventually tho.
Make mistakes, get messy, etc.
I love Arch, but it is a demanding mistress. If you get behind on updates, you're asking for pain. Also it can be very disruptive to suddenly get a new major version of Gnome that breaks extensions you used, or applications, etc.
What we instead should say is not that Arch is "unstable" because I agree it's not, but rather that Arch requires a lot more care and feeding and if you don't do that, it can lead to instability
I switched to Gentoo and it fixed all the issues I was encountering with Arch, and was more stable. Now I'm on NixOS, which is far more stable than Arch or Gentoo were.
Now, that said, the way SteamOS uses it, I don't see any issues. With an immutable system, A/B updates, and tested images, the compatibility and update issues are solved. Using flatpak for user applications solves the rest of the noted issues. Would be ideal if I could install with Nix instead of Flatpak, but ran into some trouble there.