You probably have not seen yet, but that I've been doing live pair programming sessions for a while now. I even make them live and public so you can also see how it is being done. (And I have a lot more scheduled already.)
I think this is an excellent way to learn something new, to introduce someone to a code-base, to have more cooperation among people.
I really hope that more programmers will pick up the idea and start experimenting with it.
You don't have to be expert in the subject. It is totally fine to search for answers while working in pairs as well.
See a lot more about pair programming
You don't need any special tooling. Just a zoom (or similar) session.
You don't have to record it and make it public. That's just extra perks.
For example comment here that you are interested (maybe with a link to your GitHub/GitLab repo or with a few words what are you interested in).
Then if you see others who post that they are interested contact each other and discuss the details.
Tell them you'd like to contribute to their library X and ask them if they would agree to pair program with you on the subject? Maybe they will.
Oh and you don't have to pick the author of the most popular package. Pick someone who is relatively unknown.
For Python check out my PyDigger project. If you'd like to contribute to that, talk to me.