It's a packaging issue in the image. If you download dt-blob.bin and replace the current file in /flash it should work fine. At least, I have normal stereo output here, a cable needs to be acquired to test the optical output.
Thanks, that fixes it nicely. I have analogue audio and optical audio too.
If you fix the package, I will reload Five Ninjas version then do a complete update to yours so we can verify the package is complete.