This would solve a major issue with SteamOS. The SteamOS itself is immutable/read only as you know. This means, one cannot install or make changes to the core system (it is possible, but that is temporarily until update will revert those changes back). That is why we have the Flatpak support. But many software are not available...
This is probably not something I will make use of at all in the near future but I still absolutely love that they are doing this! Valve is really carving out a path forward for linux as a whole and eventually normal folks - not just enthusiasts - will be able to drop Windows completely.
You’ll Soon Be Able to Install Nix Packages on Your Steam Deck (linuxgamingcentral.com)
This would solve a major issue with SteamOS. The SteamOS itself is immutable/read only as you know. This means, one cannot install or make changes to the core system (it is possible, but that is temporarily until update will revert those changes back). That is why we have the Flatpak support. But many software are not available...