There are distributions with a great Steam experience out of the box? It's SteamOS actually a good choice? Maybe isn't what you use or prefer.
A good Steam distro for me has a very mininal procedure for perfectly working controllers, client and general user experience.
Your direct test and experience are very appreciated.
Big picture mode has been updated to match the steam deck UX, too. You can pretty easily launch straight into big picture mode.
I'm not sure the process to bypass a login like I used to for my dedicated gaming desktop, though.