I spent a while trying to get eARC work with the TV and after much faff I got it to work when connected Only to a blu-ray player. Once I did that audio from the TV comes back and even the app audio works. But when connected to UK Sky HD box it stops working and cannot be made to work. I know it works with LG so its a bug in Samsung TV's because its the common factor. I tried with an eARC extractor same thing it will not work when the TV and Sky are together. I can make it work by connecting to something else and swapping it but it will not carry on working after TV is power cycled.
So don't waste your weekend on it - I know the cables, TV and end points all work just not together.