(Serious question. I’m not being snarky)
Covers all of the major programming languages in a deep way.
> interpreters (SICP), compilers, type systems, transaction processing, effect systems, FRP, concurrency
These subjects are the core of almost any system that you'll encounter, in practice - academic or industrial.
At least that was my experience as a self-thought programmer. The first weeks were super boring for me but also lulled me into being complacent until I suddenly found myself in deep trouble. Just because you understand the practical side does not mean you can will automatically grok the academic side of things.
I went into mechanical engineering because I had a great natural understanding of basics physics, materials, design, mechanics, blah blah. Even UC Berkeley engineering basically taught me things I knew or would have easily understood it I had to lookup that specific thing. I learned very little from my mechanic engineering degree.
I ALMOST think people shouldn't go into a major based on their strongest aptitude, but I'm not sure yet.
But definitely 100% add another focus since you'll probably breeze through the main course work.
But I dont think it should be philosophy or art or calligraphy like Jobs would recommend. I wouldn't pick a second major that would be a foolish main major.
Pick something that is a hard skill that is useful to learn and understand.
Maybe electrical engineering. Maybe industrial design. Hell, I think tons of people would be well served with what they learned with a second major in accounting.
For example, I had a second major in theatre, but I had no delusion of working a living in theatre that could compare with the kind of career that a CS degree typically delivers. It was and is a personal passion of mine, and to be able to deepen my understanding of it in an academic setting was valuable and rewarding to me personally.
Studying theatre paid dividends in other ways as well. Managing a production is a beast, and you learn a lot about how to manage people and get things done. Dramaturgy, often called literary analysis, was quoted by my professor (a scholar on the topic) as "what are the parts, and how do they go together?" -- a shorthand that I still use to this day when thinking about a new system.
If it wasn't clear already, I had a very positive experience in my studies at a Liberal Arts school, where the connections between fields, and the value they can offer each other, are a big focus.
Just taking on a second major won't necessarily pay off, but keeping in mind the holistic point of your education may create an outcome where the sum is substantially larger than its parts.
The other part, that suggests doing more courses of study is somewhat questionable.
Uni courses are designed partially to help you learn skills. But also for other requirements.
If OP wants to learn more skills, they should go for that. Whether in uni or outside. If OP wants to relax and have fun, that would also be a good use of time in your twenties.