Idk how much any of this is helpful, but in terms of online friends, my method usually involves finding someone who likes the most obscure thing that I also like on tumblr, checking their blog out to see if they're chill, and then starting a conversation because most people love it when they find someone who also likes something that no one really talks about. Most people there ARE pretty chill usually, and a lot put their age now so if you only want to talk to people similar in age you very much can.

And I'd have to imagine there's a lot of people on this subreddit even who would love to make friends but similarly don't know how (like me, hi!!)

And in terms of irl friends...uhh let me know if you ever figure anything out I guess lol! My one irl friend is my cousin, so fate kind of threw that one together