Comment by kokada
At least for Bazzite, Nobara and CachyOS, there is the SteamOS desktop option that boots directly to Steam's Big Picture that is quite unconventional in some ways (e.g. this desktop mode kinda also acts as a display manager, so there is the option to boot to your desktop from Big Picture mode and this option is generally broken without specific integration with the session manager).
Sure this could probably be a package in a more "traditional distro", but I'm almost sure most people don't expect their Display Manager to be replaced with Steam when they install a package.
> Sure this could probably be a package in a more "traditional distro", but I'm almost sure most people don't expect their Display Manager to be replaced with Steam when they install a package.
You can add steam big picture mode as a session type which would let you pick it from the login manager (the same as if you had both GNOME & KDE installed, for example). There would be no need to replace anything.