Get out of Nostr world. Bitchat is useless save for local mesh network communication, and is extremely poor for locational privacy due to always having Bluetooth LE always on. Nostr DMs and White Noise basically shotgun your metadata across a bunch of relays, poor for timing analysis, giant metadata leaks. SimpleX is the golden goose with ephemeral one time chat links and multi hop asymmetric chat relays. It has nearly impeccable metadata obfuscation. Session is pretty good, a good chunk better than XMPP mainly in metadata obfuscation from individual relay runners and from a network observer. XMPP is okay, good e2e but only when OMEMO is enabled. Poor metadata privacy from a network observer and from a server operator. Really good for LAN messaging though, and a super simple protocol, easy to integrate aside email servers since addresses are of the same format. Matrix has a bunch of known issues relating to metadata and data leaks and has the same weaknesses of XMPP. Signal has WhatsApp UX with strong encryption guarantees and some degree of metadata obfuscation. Big weakness in the phone number requirement.