So, I just saw this bit in Marginal Revolution, surprised that farmers could have successful YouTube channels. I don't get the surprise. I was aware of multiple videos from professional cleaning service companies, and those aren't even the biggest channels in the niche.
Of course there are tons of non-MOOC purely recreational math channels, the best of which are probably Mathologer and 3Blue1Brown, but there are also all manner of science channels. Non-fiction in general is very well represented, because it only requires research and a camera.
Everyone knows cooking channels are mega-huge on YouTube, and probably the safest route to fame and glory, if you have the patience for it. But have you seen Tasting History, which uses cooking as a lens into stories about the past? There are people doing honest to god science or just silliness, communities that have been around for more than a decade, and not just video essays about pop culture (very common), but video essays about pop culture meant to teach ideas about economics.
I've seen stunning art, animated simulations, talk about the long-term future and safety of AI, hilarious British game shows, and a guy who just tries to see if various liquids make good soft serve ice cream. If you can't find something at least slightly niche on YouTube, then, as one very thoughtful film critic would say, you have boring taste, and I don't want to be your friend. At the very least, you can find the video versions of a lot of good podcasts.
I have friends and family on YouTube, making videos that are quite good. It's a strange place, and allows a strange level of discovery and kismet for newer video makers. Don't get me wrong, HBO has some great stuff, lots of streaming platforms do. But if you don't dig into niche culture at all, then you're really missing out. Find something made for someone just like you, and love it deeply. Life's too short for the trivial stuff.