Is it that popular? If any provider like WhatsApp decided were to federate (I assume the goal is to get existing providers to federate and not convince every single person of your new protocol) it would essentially make Matrix irrelevant.
And I don't see WhatsApp adopting a custom protocol like Matrix, especially since they already run on fork of ejabberd and XMPP is the established IETF internet standard. The same thing applies to Google, Facebook, Zoom, Jitsi, etc. which all use or have XMPP experience for their chat products.
Some of these have changed their Code so much in relation to XMPP, I’m not sure how much it matter that they use it. FBM never could do XMPP group chats. Not once in its dozen+ year life.
Google and FB purposefully removed federation, so it doesn’t make sense for either of them to add it. So WhatsApp is out.
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I wasn’t saying WhatsApp or any chat app specifically should implement Matrix natively. I don’t trust big tech. I am saying, Matrix works well enough and isn’t dependent on the whims of big tech.
And I don't see WhatsApp adopting a custom protocol like Matrix, especially since they already run on fork of ejabberd and XMPP is the established IETF internet standard. The same thing applies to Google, Facebook, Zoom, Jitsi, etc. which all use or have XMPP experience for their chat products.