I’m facing this issue only from last few weeks. All I get is stereo pcm when watching 5.1 content. No issues with Atmos content.
Samsung qn90 with Apple TV 4K, Arc, Sub, 300s. Arc is connected via hdmi eArc to my tv.
Apple TV audio is set to Auto/Atmos. Sound is not right when I change Apple TV audio to ON ( I hear voice from surround and not from Arc).