My favourite ones are already linked: Sapolsky, Feynman, SICP. So here are some lesser known ones to signal boost:

Introduction to Cryptography by Christof Paar, I wanted to understand Bitcoin's secp256k elliptic curve on finite fields: https://youtube.com/playlist?list=PL6N5qY2nvvJE8X75VkXglSrVh...

The Maths of General Relativity by ScienceClic, I wanted to understand clearly Einstein's field equations (what the hell is a Ricci tensor) without having to read a book: https://youtube.com/playlist?list=PLu7cY2CPiRjVY-VaUZ69bXHZr...