Community college. Took a few classes I never would have normally chosen like art or acting. I was a stay at home introvert who was way past college days, so I couldn’t figure out how to put myself into social situations. But I do like to learn, so signed myself up for some night classes. Ended up dating a few people, made new friends, and married one of them. Night classes bring in the adults who have to work during the day, a few kids too, but I met just about every age group from young to very old. Study groups, group projects, anything that will involve working with or helping classmates, or anything that you think is interesting really. Have life long friends now because of that decision.
Go back to where you first learned how to make friends, go back to school.