4k Blu-Rays playing Multichannel PCM 5.1? Should be Atmos

I am having issues with my 4K UHD Blu-Rays playing full Dolby Atmos on my current setup. I play use PS5 that is connected to my Samsung S90F. I have Beam (Gen 2) and SYMFONISK rears that support Dolby Atmos (when streaming or playing games, I have no problem with Atmos.) When I start playing an 4k blu ray with an Atmos track (in this case, Dune: Part 2), my sonos app is saying that it is only receiving "multichannel pcm 5.1" when it should be receiving Dolby Atmos. I saw people suggested selecting "pass-through" on my Samsung TV but this did not help. Any suggestions on what might be going on?