When I watch 5.1 movies on Netflix I get proper 5.1 audio. My Netflix plays on Nvidia Shield, connected to TCL, and the TCL is connected to Vizio soundbar. All three HDMI.
There must be some issue from your 3080 to your TCL/Soundbar. With all the audio DRM it can be an annoying issue to deal with. Do some digging around on forums.