We will be using vMix remotely and would like the headphone feed (to where I am, remote from the vMix PC), also using remote cameras via NDI which works well. So far, this is working beyond my initial expectation.

I've set Settings / Audio Outputs / Headphones to NDI (Mains and A / B to None).

For testing, I've been using the NDI Video Monitor app that also supports audio along with the video channel for testing. However, this app seems to need a video stream, not just audio only. NDI Video Monitor doesn't even show the vMix Headphone NDI source as available.

Is there an NDI Audio only monitor application available, that doesn't need a video channel?

EDIT: NVM, you have to go into External Settings (External Output / NDI), and under NDI enable Audio Outputs as well (and set Headphones to NDI). Now I see it available in the Newtek app and hear once connected.

not yet