so i just bought a tcl 65" roku tv. when i watch tv via sling or prime i get no 5.1 surround. when i watch digital movies via plex i do get 5.1 surround. previous to this tv i was using an external roku box and i would get 5.1 surround using ALL apps. i have tried different audio settings and that has had no difference. i'm using the same stereo receiver (sony str-dh750) which supports arc and dd+.
because the only real difference is using built in roku vs an external box, deductive reasoning says it's a roku issue, and not a tv or receiver issue.