Having the same problem - the only output choice that appears is "Internal Speakers" - though hitting the ? button in the sound preferences box gets me this :
"Select a device for sound output
To listen through your computer’s built-in speakers, select Internal Speaker.
To listen through your display’s built-in speakers, select Display Audio.
To listen through speakers or headphones that are connected to the headphone jack, select Headphones.
To listen through external USB speakers, select your speakers from the list.
To listen through another audio interface, select it from the list."
BUT there is no other choice listed except "internal speakers"