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 not sure what the standard for large vs small hands is, but I haven’t had issues with pretty much any controller except the OG Xbox controller:
My kids have no issues with either the Xbox 360 controller or DS4 controller that I have.