Other than occasional captured lectures, everything 'educational' on YouTube seems to me to be optimising for that TED-style sense of wonder / happy familiarisation with the content, which is poorly associated with learning outcomes.
Covers Quantum Field Theory and General relativity in as approachable a manner as I imagine is possible while still going deep into detail: https://www.youtube.com/c/viascience/videos
Theoretical machine learning, Information theory and probabilistic inference: https://www.youtube.com/user/mathematicalmonk/videos
Heavy emphasis on analysis and measure theory: https://www.youtube.com/c/brightsideofmaths/videos
While ScienceClic's coverage of differential geometry topics is mostly a thin vertical slice of the subject, it covers it with incredible visualizations and pedagogical approach: https://www.youtube.com/watch?v=xodtfM1r9FA&list=PLu7cY2CPiR....
https://youtu.be/5ESJH1NLMLs "Children of the Magenta Line" by Warren Vanderburgh https://youtu.be/YvEB05xdAy4 "Total Synthesis of Vitamin B12" by RB Woodward
You may tell me I'm cheating by posting videos that are obviously not "native" to YouTube, but YouTube was the way I found them, how I watch them, and how I share them with other people.
OK, so YouTube-native videos are hard mode. Try https://youtu.be/WHASYE2e5Xo I suppose? I like it. It has life lessons I'd argue are at least as valuable as the videos you're thinking about.
Kling is building an operating system and a web browser, and frequently relases videos about the work. Most go through development of a single feature. The videos are unedited to show all of the development steps: design, implementation and debugging. A Masters program usually has more theory and larger scope, but this is more hands-on and in-depth.
Math and art are thing I like, just keep hard blocking stuff you don't like and upvote stuff you do.