To avoid confusion: this is not the microkernel inside Redox OS, I presume?

No, nothing to do with Redox OS. It's instead the successor of Resea and HinaOS, which were written in C by the same author. He even wrote a book about microkernels featuring HinaOS. He also wrote a tutorial which was recently posted on HN: https://news.ycombinator.com/item?id=42631873

This is super cool! Good job!

Would love to see a shell working on it.

Any idea of hardware requirements?