Some things I find by searching for very specific things, like say YouTubers in Thailand or (lately) modular synthesis which led me to Andrew Huang[0]. Other stuff I get pointed to by friends, eg Mark Rober for his anti theft videos which are hilarious. And some things are YouTube suggestions, the algorithm seems pretty conservative but it has turned up a few good things.
There is great stuff out there, I find the amount of garbage I actually see and have to skip over is pretty small these days.
[0]: https://youtube.com/c/andrewhuang