https://github.com/EtchedPixels/FUZIX#what-does-fuzix-have-o...
To be honest, I still have no idea what I'm looking at.
Fuzix is a very simple UNIX clone (and a for of UZI) started by Alan Cox, an ex-Linux kernel developer) as his retirement project.
It aims to run on old CPUs like Z80 and on microcontrollers. I found it when searching what OS can I run on the $4 Raspberry Pi Pico.
https://codeberg.org/EtchedPixels/FUZIX last updated 4 days ago
Alan's currently putting most of his energy into the compiler. It's a C compiler in C which can compile itself, and compile FUZIX, for 8080 and Z80 targets. The goal is to make it compile itself on all the platforms it can run on eventually. :)