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
Do you remember the old Xbox controllers that had the attachable keyboard? It's essentially just that kind of shape. So you would use the controller and kind of ignore the touchpads on the bottom unless you actually need them, then you just move your hand down and use the touchpads for something like mouse control. I doubt the intention is for you to use all of the inputs at once like you would an Xbox or PlayStation controller.