I have now pushed some work-in-progress code to a camera2 branch GitHub - sailfishos/droidmedia at camera2. Currently viewfinder and still image capture works as do most of the camera controls. Various issues still exist in the code such as in correct colors in viewfinder (appears to be BGR vs RGB issue) and flash not always working reliably. Video recording is completely unimplemented at the moment and I will look into that after I try to fix the current issues in the code.