This is exactly the main problem of why Linux has not already became much more popular - too many distros.
Devs don't agree on something - they create own fork. Such approach is the worst nightmare of hardware makers.
Yeah, I know some distros share the same base (Debian, Arch, etc.) but still, there are too many of them.
Every day some people are born, some die. And apart from that, every day a new Linux distro is made as well.
Since Valve is directly cooperating with Archlinux devs, this is probably the best way to go if you want to achieve maximum SteamOS support.
But I have seen with my own eyes that even Debian-Ubuntu-based Mint is doing pretty well with Steam games. Proton does it's job.
Anyway, people, if you want to go with Linux, choose something popular backed by good community.
I can assure you that, unlike Windows 12 is going to be final final final final version of Windows 10 (11 and 12 were not suppossed to exist),
there won't be more than 2 major versions of SteamOS. Because when it comes to games and software, GabeN can't count to three and above.