You’ve nailed most of the curation, but the way I get new recommendations is that I search out new stuff on YouTube. At this point if there’s any subject matter I’m interested in that’s not political or social issues, I’ll do a search on YouTube in addition to my other searches (Google, Brave Search, Reddit, etc.) to see what I can turn up. This often nets me additional recommendations down the line, often when there’s a new video on that subject posted when I’m not expecting it.

Low quality videos also get nuked with prejudice from my history.