I’ve just done a port of CP/M to the 6502 — for, um, reasons. It currently runs on the BBC Micro (or Master, or Tube second processor) and the Commodore 64.
It should be really easy to port to other 6502-based platforms; the BIOS only has like five proper system calls. It’s all written in assembler but there’s llvm-mos toolchain support so you can write programs in C. Binaries are portable across all CP/M-65 platforms (but it won’t, of course, run 8080 or Z80 CP/M software).
What’s more, I did it all on video, so if you’re very bored you can watch me write it! It’s fourteen episodes, and about 45 hours total. Good luck.
(Also, has it really been a year since my last website update? Wow. It’s not like I’ve stopped doing stuff…)