Oh man that’s the old SteamOS 2.0 from 2015.

Valve completely rebased and revamped it in 2022 for the steamdeck. Steam OS 3.6 is the current version and only available for the steamdeck.

There’s no ISO.

It doesn’t include the Playstore per se, but it does provide an installer for a sandboxed Playstore.

Give Grapheneos a try!

Posting from my Oneplus 9 Pro running LineageOS as a proof we do exist! There are dozens of us. DOZENS!

The problem is vendor support. As soon as a device stop receiving OS and baseband security patches, it becomes potentially insecure.