Union-find is the topic of week 1 of Algorithms 1 (Coursera). Here are some videos about it for anyone who might not be going through the course but who wants to discuss it at a meetup. I haven’t watched all of these yet.
I clicked through to his channel and it looks interesting.
There are also some by the teacher of that other Udemy course I bought (C/C++ algorithms).
I’m not sure yet, but these might be some of the videos from the Udemy course.