https://www.mccme.ru/dubna/eng/ (a summer school aimed at teaching advanced topic to high schoolers and early undergrads in Russia; there are hundreds of recordings and a dozen of edited notes from the school available in Russian)
As this answer got upvoted, I collected some Dubna’s courses read in English, for which recordings are available (look for “Доступны 4 видеозаписи курса.”)
https://web.evanchen.cc/napkin.html
https://t.me/mathtabletalks (in Russian)
https://www.mccme.ru/dubna/eng/ (a summer school aimed at teaching advanced topic to high schoolers and early undergrads in Russia; there are hundreds of recordings and a dozen of edited notes from the school available in Russian)
http://math.jacobs-university.de/summerschool/ (European version of above; don’t know much about them adding just in case)
As this answer got upvoted, I collected some Dubna’s courses read in English, for which recordings are available (look for “Доступны 4 видеозаписи курса.”)
Computations: from Turing machines to Tilings
First glances at the principles of Statistical Mechanics: what are Gibbs measures?
Groups, trees, and ends
Topological methods in combinatorics and discrete geometry
Thanks! The first link is especially awesome!