I have bought Samsung QA65Q70AAKXXT but I cannot use eARC. Even if set as recommended by Samsung, it do not work. Sometimes, if you turn the TV off and then on, plug the 8K HDMI cable back in, the TV will automatically search, sometime it will work, but sometimes it won't. However, when turning it off and on again, it won't work again.
Also, the firmware of the TV cannot be updated because the letters are faded and can't press select it.
At last I use optical port. This is bad experience.