Ask HN: Pre-existing API and Client for custom social media/RSS reader

For fun and for personal use I want to make my own social media/rss reader solution that aggregates data from various sources and applies my own algorithm to it. I’m a Java developer and I’m comfortable pulling together various APIs and saving it into my database and coding up the algorithm. Where I’m weak is front-end. I’m hoping to find an API I can implement such that I can use an off-the-shelf client. I’m thinking like a mastodon client, or tiny-tiny-rss/google reader/feedly or maybe even JMAP.

For the record, the “algorithm” I had in mind is inspired by my usage of the highly configurable podcatcher BeyondPod. One can configure playlist autogeneration with various rules. It allowed me to put my favorite stuff and timely stuff at the top of the playlist so I never missed it or fell behind on it, and then anything else would automatically get cleaned up when it aged out. So it’s sort of the best of both worlds of a typical RSS reader for not missing the stuff you want to follow closely, but the ephemerality/guilt free nature of social media where the excess stuff doesn’t pile up and guilt you with a big unread count.

It’s just for me personally so I figure I can bypass anything difficult to implement by letting services like IFTTT and Feedly do the heavy lifting. For instance Feedly generates unique email addresses for signing up for mailing lists and reading them like RSS feeds, so there’s my email ingestion right there.

If I don’t find an API simple enough to implement myself, I could run an instance of say TT-RSS and have my service muck around in its database or talk to its API to populate it and clean things up.

I like to read long form content on my Kobo ereader via Pocket, so I’m also imagining a solution that aggressively adds and removes items to get them displaying in the order I want and cleans up stale stuff.

What APIs exist that most closely match this use case?

How would you approach this? What snags do you forsee?