I also took the class that uses this OS at MIT. Absolutely fantastic. I was just browsing the class website today actually, and you can totally kinda take the class yourself. The site has all the lecture notes, the labs, and even a version of xv6 in a repo with branches for all the labs, along with instructions for getting it all working yourself. It's kinda amazing how open it is.
The first lab: https://pdos.csail.mit.edu/6.1810/2023/labs/util.html
I do plan to work through the whole thing myself again at some point soon.