I've been learning enough to stop relying on the Linux kernel. All Mu really needs so far is to print to screen and read from the keyboard. Here's a video about achieving that:
https://archive.org/details/akkartik-2min-2020-12-24
It seems such a small thing. But I needed lots of help, as you can see from the additions to my credits: https://github.com/akkartik/mu/compare/670cbb3d33807efb2d5e0db9e54ffed42f7ef0e3..main?short_path=b335630#diff-b335630551682c19a781afebcf4d07bf978fb1f8ac04c6bf87428ed5106870f5
Main project page: https://github.com/akkartik/mu
📷 bootloader.png