I have a Sony STR-DH520 amp, and the Raspberry PI only ever sends 6.1 sound when using LPCM.
6.1 shows an indicator of a channel in the middle rear, instead of within the two speaker indicators for left/right at the read.
The amp can receive 7.1 LPCM from a Blu-Ray player (set to send LPCM not DTS /DD etc) - all the speaker indicators light up. Passthrough of 7.1 TrueHD from the PI also works.
I'm sure that once upon a time 7.1 LPCM used to work from the PI.
It's quite possibly down the the Raspberry PI OS - this also happens with the speaker-test from the command line, and also from an install of OSMC, but I'd appreciate any help with either configuration or directions to the correct place to report it.
Many thanks for any help anyone can offer.