@laika Technically, encryption in both #XMPP & #Matrix is stapled onto the plaintext protocol (with secure transport to the server, typically).

Most commonly in XMPP with #OMEMO (https://en.wikipedia.org/wiki/OMEMO) and #Olm & #Megolm (https://matrix.org/docs/guides/end-to-end-encryption-implementation-guide) for Matrix. The clients are just better at first-class support & server owners less dickish & anti-privacy.