[maddiesdad15]

I've seen a handful of references to "selecting" audio streams during playback. I've yet to see the audio stream row anything but greyed out. Currently running Jarvis RC2, and previously ran Helix and Isengard. Assume there is a setting I have yet to encounter. Any guidance would be appreciated

[Atreyu]

It seems like you found it in sound options.
If the stream is not carrying multiple sound tracks the option is limited to 1 and thus greyed out.