Atmos reception seems to be (obviously) hardware/platform/software related, with a specific combination of requirements to satisfy (most at the whim of the streaming vendor).
I have an older LG plasma upstairs with my 5.1.4 system (Yamaha RX-A3080) and receive Atmos on Disney+, Netflix and HBOMax on all Atmos-encoded material via a Roku Ultra. No such luck with Amazon Prime, despite the material advertised as Atmos. Perhaps Amazon is reliant on a 4k connection, but for me, there is no such restriction with Disney+, Netflix and the (very limited) material on HBOMax.
Previously, I *did not* receive Atmos on an older Roku 4k stream stick with the exact same system.
My downstairs 4k receives all programs in DolbyVision no problem (have not checked Atmos, but I suspect Amazon may work there.
HTH,
Gary