> You shouldn’t need to know what messaging app your friends or family use to get in touch with them, and you should be able to communicate from one app to another without having to download both.

Shouldn't you, and should you, really? Right now, if I communicate with someone on Signal, I know that they are using Signal, and I know that we are using the Signal protocol. In a world where I don't know what messaging app my correspondents are using, how do I know that I can trust the protocol?

> “This effectively means that the approach that we’re trying to take is for WhatsApp to document our client-server protocol and letting third-party clients connect directly to our infrastructure and exchange messages with WhatsApp clients.”

Ok, third-party clients, why not. Except that now, when I want to verify the key with the correspondent, I will have to see that they use some third-party client (that may not be open source and that may be sending a copy of all my messages to some server), and decide whether or not I am fine with it. In many ways this is worse than being forced to use WhatsApp.

> Meta’s app will also allow other apps to use different encryption protocols if they can “demonstrate” they reach the security standards that WhatsApp outlines in its guidance.

Which implies that instead of telling the correspondent that I'd be more comfortable talking over Threema than <whatever>, I will have to say "here are the encryption protocols I trust, can you use one of those from your app?".

> There will also be the option, Brouwer says, for third-party developers to add a proxy between their apps and WhatsApp’s server.

And now it's not E2EE anymore, is it?

I really fear that in practice, it will just weaken end-to-end encryption everywhere. And for what? I have absolutely no problem using multiple apps to talk with friends right now, I don't need one "super-app".

But maybe that is actually a political incentive: if you can't make E2EE illegal (in order to spy on your citizen), make it weak.