I have one on my Macan. I find it good enough and the fitting was excellent.
I went with it as my dealer said a non-Porsche fitted camera may mean difficulties for electrical warranty. They did say that was very unlikely. My concern was possible 12v battery drain if not cabled exactly correctly by someone other than the dealer.
Whilst UK cars have camera prep it isn't complete to the camera location so it's not a straight forward plug in.
There are many posts on the Macan EV forum regards alternative cameras being fitted. You may find on there where the guys downloaded the cabling / fuse diagrams. There may be similar docs for the Cayenne but more than likely the ICE versions.
I've got a Porsche camera which I've previously fitted in a Taycan and 911 - now waiting for its 3rd shot at life when the Cayenne arrives. No issues fitting the device previously but there were detailed instructions from Porsche for both cars and I haven't yet seen any instructions for the new Cayenne.
Instructions only really need to point out where the factory prepared cables are hidden, so if necessary I'll go fishing!