ARC system "Stereo PCM" when it should be Dolby?

Hey Gang! 

I have a SONOS Arc system currently as my main TV Audio set up:  The ARC is connected via eARC from my 2021 LG G2 77” panel.  For the rear surrounds I have two SONOS Five’s, and a Sub to round out the “Atmos” system.   The two inputs i have for watching content are 1. AppleTV 4K (primary) and 2. a Panasonic DP-UB820 4K disc player (for films I really love and want to have great sound/picture).   I have had no issues with the sound output fro the AppleTV, but with the Panasonic Player, if it’s encoded to 7.1 (using the Arrival - the Amy Adams one - 4K disc as an example), it only outputs to “Stereo PCM.” Looking at the sleeve it’s encoded to 7.1 so I am assuming this might be the issue. 

The other native audio tracks on the disc are unhelpful since the Dolby 5.1 is ‘descriptive audio’ which I don’t need.  My other discs (Dune, Blade Runner 2049, MCU films) are all out putting correctly.  Wondering if there’s a solve?  Conversely, when i watch Arrival on AppleTV (the version I purchased)  it outputs at Dolby PCM 5.1 which is better but not ideal.  I’d like to have 5.1 on the disc, so curious how I can make that happen.  All systems are running current OS and I verified that yesterday (disc player, AppleTV and LG G2)