The results were...interesting!
I used the linked img.gz file you posted with and the MINIX DTB from the resulting SD card. Note that the latest DTB file posted in the LibreELEC 8.2 thread didn't work.
With your modified kernel, I do get 7.1 PCM @ 48khz at the receiver! But the sound is wrong. I get sound only about half the time, cutting out every 1 second or so. The pitch is also way too high, and it sounds like the actors are chipmunks. Which was hilarious in the drama-filled scene I tested with, but I digress.
What other information can I provide to be of help?