SimpleX

One of the nice things about Simplex, is that like Nostr, it is a protocol and it is decentralized.

Its grace lies in that when you send your contact, you have the ability to decide which server will be used for receiving messages, it can be that of a third party or your own, besides being able to choose a different receiving server for each contact.

Sincerely with this protocol are not necessary p2p applications where everything works slow.