Probably any of the education-specific tools that are maintained similar to enterprise software platforms, where they add 'online video tutoring' capabilities to check off a feature/table-stakes box, but it has a painful UI that makes OBS look like a dream to use, and adds an extra few thousand dollars to the school's bill every year.
At the university I work for they use Teams, Blackboard and Echo360. I do know of some people in maths schools using OBS though.