If you are using a video player that doesn't allow you to switch between the standard audio tracks, you can make a quick edit to your Headphone Dust MKV file to force the Dolby Atmos TrueHD track to be the standard default track.
To do this, download and install the free MKVToolNix app and drag your Headphone Dust MKV file into it. Select the Dolby Atmos TrueHD audio track and drag it up so that it's the first track in the list of audio tracks, set your output file destination and hit Start Multiplexing.
It will create a new MKV file for you with altered settings that force the Dolby Atmos TrueHD track to play by default.