Not the OP but the courses I took on operating systems (writing a simple one, in C) have yielded lessons that I've used throughout my career. If you can find a

Not the OP but the courses I took on operating systems (writing a simple one, in C) have yielded lessons that I've used throughout my career. If you can find a course too challenge you, and it's taught well, that should provide a ton of the learning that us old neckbeards couldn't avoid back in the day. Forcing yourself to use barebones languages and environments is good too. Hacking on ancient machines or targeting embedded hardware is another good way to get a better intuition on the order of magnitude performance differences of various approaches. Reading about promising tech of the past is also useful: prolog, Smalltalk, etc. Lots of inspiring and fruitful lessons to mine there.