The back up service is optional, but Signal still collects your name, photo, phone number, and worst of all, your contacts. That is not optional. There is nothing you can do to stop it. That information will be collected and stored in the cloud. It's also exactly the kind of information Signal used to brag about not being able to provide to law enforcement because they never collected it in the first place. Well, now they do collect it, but they never updated the webpages that they wrote back when they didn't to reflect the new reality, just like they never updated their privacy policy.