The combination of this TV using Google TV and this soundbar didn't work properly when I first connected them via HDMI ARC. The TV would set up the LG soundbar without issues and work correctly untill the TV power was switched off and then later on again. After the TV had started it would switch every few seconds between using the "TV speakers" and the digital "Audio System".
The LG sondbar could instead be connected via Blutooth rather than HDMI ARC but the range of volume when doing so was limited. Alternatively the LG sondbar could be connected via optical cable but then the TV remote volume buttons would not control the volume of the soundbar.
This meant that the soundbar could be connected via all three of its inputs, HDMI ARC, Bluetooth or Optical cable, but none of these connections was fully functional. I contacted Sony helpline about this and they acknowledged the issue but did not offer a solution.
Since the issue of the sound cycling between TV speakers and the soundbar occurred after powering the TV on I thought that the issue must be related to the HDMI CEC function of the TV turning the soundbar on and off. I was unable to disable HDMI CEC on the Sony TV but I found that the soundbar had an option to turn its "Auto power on" function either on or off. I thought this must refer to HDMI CEC, so I turned off this function on the soundbar. I then found that the cycling problem did not occur any more when the TV was turned off then on again, but the TV was using the optical oputput. So I connected both the HDMI ARC and the optical input from the soundbar to the TV with the "Auto power on" function of the soundbar switched off and I switched the soundbar to use optical input.
This resolved the problem. The TV could be set to "Audio System" rather than "TV Speakers" the soundabr would deliver the audio, and the TV remote volume buttons controlled the volume on the soundbar.
I posted this description because when I contacted Sony helpline about this issue they acknowledge the issue and indicated that it occurred for a number of soundbars, not just the LG SN4, and that a number of customers had reported the same issue to them. Perhaps my work-around solution may be of help to other people.
It’s nice of you to post this for anyone facing a similar issue. 👍