I just had a fun idea that might not take too much time to implement and could work on your own computer (not 100%, but probably more privacy friendly than using YouTube directly):
have a powerful AI companion API, such as ChatGPT 4. The most up-to-date with the world data the better it would work.
write a script that gathers your favourite channels, the last 100 videos you watched, and whatever other useful data you feel could serve as "food"
send a prompt to the AI asking for "give me 10 interesting YouTube search queries related to the following channels/themes […]"
use multiple Piped/Invidious server APIs and query these and gather the most common results + the top X results or each query.