Looking at the course listing for UNH ( https://ceps.unh.edu/computer-science/program/bs/computer-sc... ), I'd suggest auditing (I imagine that's cheaper if you're not looking for a degree?) some of the following: Data Structures and Introduction to Algorithms, Assembly Language Programming and Machine Organization, Introduction to the Theory of Computation, Operating System Fundamentals, Algorithms, Programming Language Concepts and Features, Compiler Design, Systems Programming, Formal Specifications and Verification of Software Systems. Those are the ones that look like more formal CS, and gets you into at least an intro to fun formal/theory stuff like automata, grammars, low-level programming, functional programming. Performance Evaluation of Computer Systems and Mathematical Optimization for Applications also look fun to me, or you may be interested in some of the other electives too like Computer Vision, ML, etc.

If that's local, affordable, and easy, I wouldn't worry too much about looking for something "fancier" right off the bat, I think there's a lot to sink your teeth into there. There's a lot of stuff online too on all these topics of course, but if you're like me, that's not the same as taking a live course.