Bazzite works a bit differently as it's an immutable distro. Whilst updates for normal/user-level packages (Steam etc) will continue to work (as these are Flatpaks), your core system packages won't and you can't just change your repo to say Fedora's repos, as system updates are image-based and are pulled directly from Bazzite's github repo (which in turn pulls from Feodra).

The good news is, you can easily rebase to any other uBlue or even Fedora Atomic distro with just one or two commands, or if you're technical, you can even fork Bazzite's repo and build your own Bazzite (they even provide instructions on how to do this, it's very very simple, relatively speaking).

Steam is not a flatpak on Bazzite.