I really would like to get Valve interested in NixOS (or Guix), because it really is a much better foundation for what they are trying to do. Especially when juggling old precompiled games, it's essential to be flexible with multiple versions of libraries etc. But e.g.

FlatPak is just that, which is the pendulum swinging too far in the other direcition when you want the Steam Deck Steam OS too still be a coherent experience outside specific games.

The proof of that latter is simple: any fedora silverfish-like pure flatpak thing is still vapourware at this point, where Nix and Guix are production-ready, and very self-contained so one can be sure they aren't going to suddenly fail outside of your control.