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
I’m a bit too lazy to check for the entire stack I admit but I bet a lot of those actually do. Still to do a quick check Google for examples is on https://ev.kde.org/supporting-members/