I had no idea there was an entire OS written in Rust that was this far along. Is all the bootstrapping from assembly directly into Rust, or do they still have a dependency on C and gcc just to get things going?
There are pure rust, no c, embedded RTOSes, like Hubris.
Here, make your own "kernel" in a few lines: https://rust-osdev.github.io/uefi-rs/tutorial/app.html