I haven't checked in detail, but I would suppose SteamOS isn't far off from running on general-purpose PCs. Else, I've heard a lot of good things about Bazzite.

Nvidia drivers leave a bit to be desired on Linux imo. I’ve got an all AMD HTPC right now and bazzite is terrific.

SteamOS does run on regular PC’s I believe unless something has changed?

Why do you have to install Windows? You could put bazzite or any other distro of your choosing on this machine and have a similar experience to the official Steam Machine.

I thought bazzite wasn't running against nvidia yet?

It may not, but that doesn't mean you need to install Windows. Any distro that packages Steam and the Nvidia driver will work.

EDIT: It appears to be supported for RTX 20xx and newer GPUs.

https://www.reddit.com/r/linux_gaming/s/UHQ0ZiW0BX