Mastodawn

I haven’t finishing updating the piefed app wiki, but based on what you are looking for :

bell subcription
crosspost comment merge

i would say interstellar :
https://piefed.social/community/fediverse/wiki/piefed-app

Or using piefed mobile website as an app aka PWA

PieFed : Front-end and Apps

Federated, open‑source, ad‑free, and fully under your control. Build or join a community that reflects your values with no corporate overlords. This instance is run by the founder of PieFed. [Mobile apps for PieFed](https://piefed.social/post/1258559)