At this point I think it’d be more fun to port CP/M to AVR.
i thought about that but you also have to port the apps, many of which use self-modifying code, which flash program memory is not enthusiastic about
Someone on the blog post linked suggested implementing the BIOS calls in AVR code with some sort of mode switch, I guess you could go further. Port CP/M keeping syscall compatibility but use a CPU emulator for application code.
sounds sensible
the guy you're replying to got linux running on an atmega (but a bigger one)