Its very hard to do this without opening up to a lot of potential fuckups and exploits. The way e2e works is by exchanging public keys (kinda like a cryptograp

Its very hard to do this without opening up to a lot of potential fuckups and exploits. The way e2e works is by exchanging public keys (kinda like a cryptographic username), imagine having multiple devices and verifying + keeping track of the keys from each device. This is why im not surprised fb was the first to come out with this feature, you need fb level resources to get this out first and from a quick look at the article it seems like they're not using centralization to solve the problem. "WhatsApp multi-device uses a client-fanout approach, where the WhatsApp client sending the message encrypts and transmits it N number of times to N number of different devices — those in the sender and receiver’s device lists."