AFAIK the correct channel order for a 5.1 m4a is C, FL, FR, RL, RR, LFE. (I'm fairly sure ffmpeg would arrange them automatically for you when converting from WAV)
I have never used a surround M4A file so I couldn't speak about that but I forgot to add that you are correct about ffmpeg arranging the channels since no matter what surround files I load into Audacity I always seem to get the same order for each channel regardless of the file format.
Audacity does not comes with ffmpeg included, it has to be downloaded separately due to patents so it may be worth checking that.
https://manual.audacityteam.org/man/faq ... brary.html
That should sort the problem out but failing that I'm sure there are plenty of software that can do the conversion for free. Sorry I can't be any more help.
As for the album it kind of reminds me a little bit of the Volcanic Dance track from the Legends of the Lost City shows.