>>13764760Found this guy who's like 16 years old has done good vids on topology, meassure theory and manifolds
https://www.youtube.com/channel/UCIUPBxtBMQvssqSbx73t8SQ3B1B is pretty good if you just want some miscellaneous math topics, same for mathologer.
Another youtuber I can think of that actually goes over advanced topics is Richard Borcherds
https://www.youtube.com/channel/UCIyDqfi_cbkp-RU20aBF-MQHe's a former fields medalist and goes over topics like algebraic geometry and category theory.
For physics I can't think of that many channels other than university lecturers, I guess Sean Carrolls "The biggest ideas in the universe" is ok, but it's still popsci.
Other Stem subjects I can't tell you much about.