From what I understand, Signal messages should really only be considered encrypted in flight. At either end the massage could be picked up by an insecure device

From what I understand, Signal messages should really only be considered encrypted in flight. At either end the massage could be picked up by an insecure device (custom keyboard, keylogger, screenshots, etc.), and a determined hacker will be able to compromise any casual user’s phone. Still, there’s value in encrypting in-flight messages.