The Mavic 2 supports DJI Goggles version 01.04.0500 (or later versions). It’s said under the FAQ section of Mavic 2.
Current firmware I found (ussing dji assistant) was version 01.04.0400. No word, from DJI support at this moment.
No possibility to get one of the demo videos and find out what audio codec used ?
Access to flash memory ?
I tried a mp4 from sdcard. Played well but indeed no sound.