Hobbies are one of the main things for connecting people and making new friends. It's the first thing for finding interesting and close topics for discussion, of course it's usually only a beginning of a friendship but it's a perfect start for creating one... Personally I found many friends in this case, for me main things for hobbies were reading, industrial and electronic music, collecting comics and music CDs, drawing and handmade arts. Postcrossing is a very cool hobby in this case because with it you feel connection with other people from all over the world and it's amazing. I adore to participate in it, find new postcards https://masterbundles.com/postcards-creates-and-buy-online-free-postcards-templates/ with interesting design, decorate them or even make with my own hands.
I've got an amazing experience because of that in communicatoon with other people, also many new and interesting stuff for my hobbies (sharing ideas in this case is so awesome! ), many of my best memories are connected with all that things. So I think that almost all my hobbies can be considered as the constructive ones