You might want to start with something like https://en.wikipedia.org/wiki/Xv6 https://en.wikipedia.org/wiki/Xv6 , which is more designed for educational purpose

You might want to start with something like https://en.wikipedia.org/wiki/Xv6 https://en.wikipedia.org/wiki/Xv6 , which is more designed for educational purposes. MINIX3, unlike its predecessors, was not design with that as a goal.