It appears every few times I open the app and the usual android back button doesn’t make it go away, and there is no cancel button. What you have to do is toggle the toggle, then the button will change to “do not back up” and then you can press it. It annoys me how easy this makes it to accidentally turn on backup.
I can’t wait until the immich photo editor gets enabled and hopefully it eventually duplicates all the google photos editor features because that’s the only reason I keep around the google photos app.