"Compatible" is not the word to use here. If you have Intel or Nvidia hardware you're going to have tons of issues. Especially with Nvidia graphics cards where you generally don't get a display at all.
Hell, I have an all-AMD system and I would likely have issues as well, since SteamOS doesn't support GPU's newer the the RX7000 series, and I have an RX9070XT.
If you're going to insist on putting a label on the SteamOS install file, it's "unofficially available for technical support". Anything suggesting more than that is dishonest