I mean, how many channels do you need?
In general, I don't think I found most of the YouTube channels that have creators that I watch on YouTube. It tended to be on Reddit, where in the course of a conversation, people with familiarity in an area recommended relevant channels. I wasn't actively looking for them.
EDIT: What you might try doing, if you don't want to use Reddit for this, is going to a community on the Threadiverse that's relevant to whatever interest that you're looling for, and asking folks there to recommend YouTube channels relevant to the subject. Might also try hitting Google or similar to search for past references to YouTube channels on a community or subreddit. For Reddit, site:reddit.com/r/subredditname
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Kagi has a "Fediverse communities" search that I use; I don't know if anyone has yet created a dedicated search engine, but I imagine that it's good odds that someone will sooner or later.
looks
These guys purport to craft searches that work: