"Setup Icon" inside Apple ID -> iCloud
Are there others who have this "weird" Setup icon, with the option to turn on/off?
It's on both my iPhone and iPad.
It came in iOS 15.5. I noticed it was not there from the start, but as I started setting up my devices it came. I noticed that after I set up my AirPods it came. However, it may be a coincidence. As you can see in the pictures, it is between Apple's own apps, so it is not a 3rd party app.
Screenshot from iPhone
Screenshot from iPad: