https://www.cnet.com/news/apple-releases-ios-12-1-1-update-fixing-facetimes-annoying-camera-issue/

Instead of switching the camera view with a single tap (like on iOS 11), iOS 12 forced you to open the hidden menu (which blocks out the screen) then find the camera switch icon and close the menu to see if it worked. With iOS 12.1.1, the button to switch the camera is on the main screen, bringing the process back to a single tap.

The update also includes other changes and bug fixes like: