I guess this is a different SteamOS than the one that has been freely available for years?
I think what’s meant is there isn’t an official ISO to download as it’s not yet that polished for PCs
There used to be though. I have it on a DVD. SteamOS is much older than the SteamDeck.
The current, unavailable for general download, is Steam OS 3. Valve just refuses to put a number 3 anywhere, do they just pretend the other two do not exist.
BTW, there are a few “almost steam os” out there. I can vouch for Bazzite, it’s fedora based and really good. Very welcoming for beginners, but had a lot of options of you want to dig a bit.