On all Forester/Sunseeker units the camera is “supposed” to be an observation camera. It also serves as a reverse camera so I’d question why it goes off when selecting reverse. You can select the camera off mode by touching the X icon on the screen or via the “apps” mode which is selected via the center button on the left side of the radio.
Otherwise the only reason you should see the rear view display change is when selecting left or right turn signal which, if installed, will bring up the side camera view.
2018 Forester 3051S (aka Clyde)
2015 Wrangler Toad (aka Bonnie)
At some point during every day you suddenly realize nothing else productive is going to happen the rest of that day. For me, it usually occurs around 9 am.