Batch editing default audio track - mark one with specific or most channels

Hi there,

I record over the air TV shows with MythTV. Many of the recordings have a 5.1 track and a descriptive audio track. I’ve noticed when I move them to Jellyfin,
the player almost always defaults to the 2.0 descriptive audio track.

When I look at the files with mkvtoolnix, it appears that both the 5.1 and 2.0 audio tracks have the default flag set.

I’m not that comfortable writing bash scripts yet. Is there a way I can use mkvtoolnix CLI in a script to remove the default tags from both audio tracks and then add the default track tag back to the audio track with the most channels?