Folks are working on it! I believe it boots on some small systems and under QEMU, but it's still relatively early days. I'm excited for the port to eventually make it into the gate, though!

In before someone asks about riscv64 ;)

I don’t mean to downplay the importance for you personally but I do want to clarify that while it might be a non-starter for you, all of arm64 is so new that it’s hardly a non-starter for anyone considering putting it into (traditional) production.

You're right, however I was looking for the same information to maybe try it on a RPi to learn more about Illumos.