I think they focus mainly on the fact that these are federated and mature solutions. I don't know anything about Matrix but as far as XMPP/Jabber and "push notifications" go, you don't need to reveal the message, nor the sender, in the alert. Right, it's not perfect, but in my book that goes a long way for privacy.
replyYou can’t send the notification to an iOS app from a federated server. All notifications to apps on iOS must come via APNS and be delivered to APNS via mTLS with a client cert issued only to the developer/publisher of that one app. Each federated instance would need its own app.
reply