I have the same exact problem with my 8550. I have it connected via the hdmi1 port to my Onkyo receiver. I cannot get the sound through my receiver out to the external speakers. I have done extensive research on this but have come up empty. I called Samsung, awful customer support. They said they would have someone from advanced tech support call me but they never did.
I give up at this point.
I get no receiver sound when streaming Netflix to my Samsung 8550 4k tv. The receiver is Onkyo 838 4k.
I am only using the HDMI ARC connection.
Do I need to adjust a tv setting or do I need an optical connection.
I currently have to change to tv speakers to hear Netflix.

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