With Signal's default settings, Google reads your Signal messages when they come in through push notifications.
Correct me if I'm wrong.
Edit: For those in doubt, last year, I started seeing content-aware auto-reply options in my Signal message notifications; that is not a function of Signal, but a function of Google's Android. One could escape it by using a de-Googled Android like Lineage or Graphene, or by hiding the message content (which is not the Signal default) and would surely hurt Signal's adoption, when you have to unlock the app to read each message.