I took my car to have the software updated as I was missing the subwoofer settings too.
I have a 2017 FL A3 e-tron with the HDD based nav.
I took it to Audi in Hitchin who were incredibly helpful, unfortunately their first attempt failed and they had to order an SD card from Germany, with this the car updated perfectly the technician noted that it did 10 ! other updates as well but I am unsure of what these were...
The audio quality seems better too though this may just be subjective....
I can also note that now my speed camera POI are shown on Google maps and the MMI feels snappier also car play seems to be smoother too =)
The car started with an MMI version 0679 and was updated too 1168
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