Seconded! Another math youtuber who is an outrageously good educator is Adithya Chakravarthy a.k.a Aleph 0. He doesn't put out videos very often, but when he does you're probably going to learn something new even if you knew the topic he was speaking about.
He uses elegant hand-drawn notes rather than Manim - although 3blue1brown's open sourced visualization library is beautiful too, I think this makes it extra impressive.