How to ideate small projects which HN community find fun and worthy?

I don't think you should aim to create something they find fun and that's it.

HN should be a place to showcase what you're doing and why you're doing it. not becoming the center of attention for your creations.

A version of this, https://hckrnews.com/ , with nightmode and filters would probably get you some upvotes, but life is short and I think you should focus on something that makes you money or your relationships, not fleeting internet fame.