For the record, XMPP has OMEMO as its standard E2E/PFS-preserving encryption protocol (based on your usual double-ratchet aka Signal encryption), which is regularly audited for security (and as recently as last month in the case of the Conversations Android client).
XMPP being used by several law enforcement agencies and institutions like NATO, I wouldn't default to making fun of its security.
This is such a non-argument. Every non-toy XMPP client supports OMEMO¹, so it makes no practical difference. Signal only supports one single official client and will cut you from your account if you happen to have ergonomics, accessibility or platform preferences that are not supported by Signal. That's the price to pay for Signal's "universal defaults", and that's a tough one if you ask me.
XMPP being used by several law enforcement agencies and institutions like NATO, I wouldn't default to making fun of its security.