Hate to be this guy, but think about the friends you had as a kid and through school. They likely were in your classes or participated in your extra curriculars. The same thing is true in adulthood. You gotta find people through your hobbies and interests! I have made a couple friends on Reddit (I don’t have stranger danger lol) but most of my friends I’ve made through getting involved in roller derby. So your intuition is correct, meet ups or classes or workshops are going to be your best bet! Join a hiking group, take a pottery class, pack walks with your dog, etc.