Sabayon Linux. I’m not sure if it’s still releasing updates, the main website is dead. It was based on Gentoo and later funtoo, but had a package manager of precompiled binaries. You could still use emerge if you wanted to. Definitely a weird and interesting distro

Blend OS is trying to do the declarative nixos thing but with an arch base. That’s pretty cool.

ClearOS was Intel’s attempt at an immutable os. From what I remember it was really fast.

Edit: actually it clear Linux not clearOS. Edit: also clear Linux is stateless. I don’t know, there’s a lot about it I don’t understand