Well that was the dumbest explanation ever, that’s basically just political pretext to give the government contract to some french company. Potentially there has been some lobbying going on.
Signal doesn’t store it’s encryption/decryption keys in the cloud, so you would need the devices and then you would still have to decrypt content if the user doesn’t give you access manually.
To crack a 128-bit AES key, it would take 1 billion billion years with a current supercomputer. To crack a 256-bit AES key, it would take 2^255 / 2,117.8 trillion years on average.
So until some amazing quantum computer comes along, this is pretty safe. Fuck Olvid.