The upcoming 4.21 release (in preview right now) has an experimental version of the audio export. You need to run it with the -audiomixer option and look for the option to enable it in the render movie dialog.
The upcoming 4.21 release (in preview right now) has an experimental version of the audio export. You need to run it with the -audiomixer option and look for the option to enable it in the render movie dialog.