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
DS4 is pretty close.
I like the ds4 - so much so that I want to get a new one and mod it for more modern features. But it’s still distinctly larger. It can be kind of surprizing to re-experience just how small and light the ds2 is compared to newer controllers.