PinePhone: back camera doesn't work with plasma-camera

First of all the plasma-camera package is missing the gst-plugins-bad dependency, that will be fixed with !859 (closed) however.

Once that dep is installed, the application doesn't complain about a missing camera anymore, but the image stays black. When taking a photo, the console reports QCameraImageCapture error: "Camera not ready"

On launch of the application CameraBin error: "Missing element 'multifilesink' - check your GStreamer installation." is also reported, but I'm not entirely sure if that is breaking anything important. This seems to be because of a missing dep on gst-plugins-good, fixed in !859 (closed).

On launch of the application I hear the camera making 2 tick noises, but that's it.