After a while of no updates to the actual ISO download of HoloISO, the creator of this SteamOS-like Linux distribution has announced the original is now dead. As it's being replaced by the newer immutable HoloISO.
This seems more in line with how these OSs should be made IMO. I understand the point of Linux is to do whatever you want with it, but that's antithetical to the point of game ready operating systems like these. Especially when your average user is gonna be less Linux literate than other distros and can easily break something. It's also not like the read-only file system can't easily be modified by those who know what they're doing.
Yeah, for a device like the steam deck that's perfect. I wouldn't want it like that for my personal PC though, just give me an old school package manager.
There still should be a more general Steam distro for people's homebuilt PC's that works more traditionally though (because sometimes you need to do something custom to make some weird device you have work).