Don’t know if collecting things is it’s self a hobby but I collect a lot of things music oriented (and I also play acoustic/electric guitar). Things like posters for specific artists/bands/albums, rock pop figurines, and my primary source of listening is through records (currently own over 50).

I’ve also gotten into programming as a hobby recently but for a very specific field, a lot of the biology tools frequently used in my field are just tedious and unappealing. So I’ve taken up the computer science field of bioinformatics as a for-fun hobby, and in creating some of my own programs and databases it also does allow me to study a lot more. Biology in general is a hobby of mine, although since it’s my planned field of work I don’t know if that still meets the criteria as being a hobby.