What I'm wondering is: where do I go on the internet to find other people who are interested in studying and discussing a particular online class? Or if that do

What I'm wondering is: where do I go on the internet to find other people who are interested in studying and discussing a particular online class? Or if that doesn't exist, should it, and could it be a good thing? stackoverflow / quora / r/math etc would still be the place for carefully-asked generally relevant questions, but it seems like it would be really helpful and motivating to have place where you could contact other people who are studying or otherwise knowledgable about the same course. It could be a mailing list, or a subreddit or whatever. Ideally it would also provide a way to put together a group of people to start on a new course. Does anything like this exist already?