Both cameras (back/front) and flashlight (greyed out button) stopped working. It is also not possible to get an image from the camera when using it in other apps (e.g. barcode scanner), the camera feed simply stays black.
OS is Android 10 up to date
I disassembled and re-assembled the phone (dis/re-connected camera module)
It may be a software issue (?) as the back and front camera seem to be separate modules and thus it makes little sense that they both stopped working at the same time(?)
One more thing, although primarily about diagnosis confirmation rather than fixing:
If you call * # * # 6 6 # * # * you should get a set of hardware tests (the tests might also be accessible through the My Fairphone app) including simple camera tests. From your thorough testing so far, it will probably only confirm the malfunction, but this test might be a good reference when you contact support.