Got it from here : https://infosec.exchange/@mattburgess/111885761552024420
NEW: WhatsApp will soon make it possible to chat with people who use other messaging apps. It’s revealed some more details on how that will work.
— Apps will need to sign an agreement with Meta, then connect to its servers.
— Meta wants people to use the Signal Protocol, but also says other encryption protocols can be used if they can meet WhatsApp’s standards
— WhatsApp has been testing with Matrix in recent months, although nothing is agreed yet. Swiss app Threema says it won’t become interoperable
Does that matter if it’s end-to-end encrypted?
How do I know that WhatsApp isn’t performing client-side scanning of messages? Meta has been doing it before, on Messenger