A completely-from-scratch hobby operating system: bootloader, kernel, drivers, C library, and userspace including a composited graphical UI, dynamic linker, syntax-highlighting text editor, network...
I figured if anywhere would appreciate this, it'd be the fediverse.
ToaruOS is a hobby operating system which has been completely coded from scratch as one developer's 12+ year long educational project. It not only features the made-from-scratch Misaka kernel, but also the Kuroko coding language. It can even run on real hardware.
You might recognize ToaruOS from jdh's Tetris OS video, where it was used as a reference source.