As of right now, I don't think there is a way to bring in ANY audio from ANY sources. The only way to get audio in is to use the external FFT that you can setup in the preferences. I know you can convert NDI to Dante and then use Dante as your external FFT. You could probably even convert NDI to a local playback source via virtual hardware and eliminate Dante all together.
The bigger picture issue I see here is that there is no audio support for sources and not just a NDI exclusive deal here. I think multichannel audio will need to come before allowing sources to bring in audio, but that's just my 2 cents. For now, I know I can bring in NDI audio with some work arounds, not ideal, but do-able