sorry, but I think what you are looking for is platforms like Lemmy. it is not centralized, it is distributed. not peer to peer, sure, but
- since a lot of devices are not being online at the same time, mobile phones but even desktop PCs always go offline for some period of time, the direct communication wouldn’t really work with a lot of other users
- you would need to store much more dataon each of your devices, unless you’re the kind who doesn’t care about mindlessly deleting past conversations
firefox can do the same with any other search engine, it has a search widget