If just recommending npubs suffices, then Plebstr kind of does this. Probably not even close to what you are looking for though.

If you are talking about an algo, then it's on us, meaning either that we have to provide that manually rn, or that we should rely on organic content recommendation or thst it's on us to develop that functionality.

Personally I am a fan of regularly diving into Global looking for new and interesting content and npubs to follow.