Phoronix article: https://www.phoronix.com/news/Steam-Machines-Frame-2026
Also listed here: https://store.steampowered.com/sale/hardware
Valve has already sent support for the new Steam Controller upstream: https://www.phoronix.com/news/New-Steam-Controller-SDL


Yeah, it’s not released or supported outside of the Steam Deck or handheld partners. So you’re probably not going to get Nvidia drivers or anything else that’s not built in to the kernel.
You don’t need it though, you can just run Steam in big picture mode on whatever distro you want.