You can install SteamOS on any machine, but AMD GPU are somewhat required if you're not up to major tinkering. Valve does not officially support NVIDIA gpus atm; they are working on it.
Easier access to SteamOS images for generic HW also appears to be in the works:
> Ahead of Legion Go S shipping, we will be shipping a beta of SteamOS which should improve the experience on other handhelds, and users can download and test this themselves. And of course we'll continue adding support and improving the experience with future releases.
> Valve does not officially support NVIDIA gpus atm
Given NVidia's reluctance to support DRM (direct rendering manager) and Wayland, plus the general levels of nightmare that their official Linux drivers are, I wouldn't say this is Valve's fault. They've already been a poor choice on Linux 20 years ago. Even Apple has always been uneasy about their relationship (while Radeon was a less powerful choice for "premium" machines).
Also consider the ongoing AI hype. NVidia is right now very busy making their GPUs do exceptionally useful work on Linux - except the money is not in the graphics.
That is for SteamOS 2. The newer SteamOS 3 does not officially support anything other than AMD hardware because the Steam Deck uses AMD hardware and their current focus is on improving support for that.
Nvidia had best in class support for linux and freebsd as a result of essentialy using the same driver across all three operaating systems. If you wanted good opengl support they were the only choice 20 years ago! Valve not supporting nvidia gpus at the moment has more to do with SteamOS on ly shipping on the steam deck which uses AMD hardware.
Yeah, if you wanted a low power x86 device (which pretty much means iGPU) then AMD is the only game in town. The open source drivers probably helped in this regard but if things were different I doubt Valve would have turned their nose up at Nvidia.
You can install SteamOS on any machine, but AMD GPU are somewhat required if you're not up to major tinkering. Valve does not officially support NVIDIA gpus atm; they are working on it.
Here's a video from Linus Tech Tips on how to do this https://www.youtube.com/watch?v=tdR-bxvQKN8 .