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 stopped building my own PCs over a decade ago because I was barely getting the parts at the same rate they would've come in a pre-built, ram was always hard to get, good deals "sold out" so quickly, and if a part goes bad it's easier to take it to a warranty repair than it is for me to fight with the vendors myself.
My main machines recently have been low power laptops, my steam deck, and my phone, using GeForce now has allowed me to play most of my games on shit hardware, and my 10 year old games run just fine (mostly) on my 5 year old laptop.