4chan

Mathloger, numberphile, computerphile, Sixty symbols: more good math/computer science theory channels

applied science, breaking taps: truly amazing "garage" engineering. They take on projects that you would normally expect to take a specialized lab.

alpha phoenix: his expertise is in materials science but he does delve a bit into electromagnetic questions

Mr P Solver: solving interesting problems computationally in pthyon

Eevblog: good electrical engineering insights with a nice Australian accent

Practical engineering: all the civil engineering questions you never knew you had

Stuff made here: what happens if a robotics expert has a generous fun projects budget and never sleeps

Tropical tidbits: discussion of the meteorology of tropical storms and hurricanes as they happen with none of the weather reporting sensationalism

I'm sure I'm missing some, but that should be a big enough list to add many hours to your watch list.

I have a physics degree, and 3 blue 1 brown's latest videos on light are amazingly presented in comparison to the vast majority of lectures I've sat through. It makes me hopeful that online video sharing can help improve pedagogy and not just be clickbait nonsense.