Not-a-Linux distro review: SerenityOS is a Unix-y love letter to the ’90s
arstechnica.com
Although it's nowhere near ready for prime time, there's a lot to love here.

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.