Ars Technica | Not-a-Linux distro review: SerenityOS is a Unix-y love letter to the ’90s
Here are links to the website, GitHub, and Wikipedia pages.
The article I linked is a couple years old but I did a quick search of the community and it doesn’t seem to have been mentioned here. Hopefully you find it as neat as I did.
There’s also a couple YouTube videos covering it if you have some time to kill.