If you don't want to use the cloud version, there's a feature to store backups locally on-device.
Signal blog: https://signal.org/blog/introducing-secure-backups/
Every app offering cloud-based backup is in fact designed to "collect and store" sensitive data. That at least is opt in. The app also collects your name, photo, phone number and worst of all a list of your contacts and permanently keeps that in the cloud and there is zero way to opt out of that data collection. No matter what excuses you want to make for them there is no getting around the fact that the device does collect and store sensitive data. Just like it can't be denied that they've added several new features none of which is reflected in their privacy policy because they've frozen it in time.
This is an app which is advertised to whistleblowers, activists, and others whose lives/freedom could depend on how well they understand the risks involved yet Signal outright lies to them about those same risks.