There's a 9legacy port, and an in-progress 9front port.

https://m.youtube.com/watch?v=EOg6UzSss2A

That's interesting, thanks. I feel a need for simple multitasking/networking OS for synthesizable RV32I core (not RTOS like, but more like Unix or CP/M). Would be nice to try Plan9 on it once port is out.

Probably not. And there aren't many 32-bit RISC-V cores with an MMU. I guess you can use a simulator if you found one.

I use one written in SpinalHDL. :-)

Next question is how much RAM it needs to boot and can it be used without rio ?