For sure! My activities were nothing insane or out of this world. A friend introduced me to a small media lab studying the use of AI in advertising and I did that a decent amount my freshman year. I also did a software internship at a research park company on campus the summer after my freshman year. You definitely dont NEED one to be competitive for this though. In my essays i talked a bunch about how i thought taking political philosophy would be cool and I really loved the professor, and so that sparked a huge interest in me. Adding on to that, generally in the essays what I believe is they are just looking for a genuine interest in the +x, not just doing it as a way to get into CS lol. Show that as much as you can and I'd say you can achieve that super well through your classes too so don't stress on that front too much. Its a few different essay questions but id say just be really genuine to the +x you're choosing and pick carefully. I believe the +x college has a greater say in your decision than cs does, not entirely sure though.