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.
Those union find videos look like they are by the same person who made these free courses on YouTube.