Hi, i am having an issue with volume not syncing between normal stereo content and high res audio.
I have an LG 55 nano90 2020 model. I work with a Chromecast with google tv.
Chromecast is in hdmi stating higher refresh rate. And Soundbar is plugged into the eArc port. Chromecast is also directly plugged in with Ethernet.
*Yes ALL my stuff is updated to latest software. (Computer nerd, build computers...have Plex server...)
At first I struggled to get the Atmos or Dolby format to play. Was only getting stereo. Finally found setting in Chromecast to allow surround sound formats and also set tv to passthrough.
*Other settings hdmi is set to bitrate and not pcm. I have tried turning eArc on and Off. Unplugged system so it could reset between swapping.
I have tried to turn off and on the CEC settings in Chromecast and or tv to see if that would help...nothing.
I don't know what else to try...i have fiddled with app settings but not much. I see there was remote setups but it doesn't pick up my Chromecast remote.
So currently i have a work around where I can use Chromecast remote for normal stuff with Sonos volume 100%...but as soon as I go into Netflix, Plex or anything that plays high res the Sonos bar is 100% super loud. Chromecast only works to mute volume...i can see slider moving down but volume stays unchanged untill it gets to zero then mutes. I have to then swap to LG remote as that then allows me to lower volume...only then later having to raise volume again when watching low res audio with Chromecast device as the LG remote only controls Sonos not Chromecast volume.
**Update**
*Sorry took so long got logged out of my password manager...took till weekend for me to try and reset my password.
So update... still doesn't work. So to just to reiterate the problem. When sound switch from stereo to high res audio it basically swap from my Chromecast device handeling audio to the Soundbar handling the audio. This means volume is either 100% when swapping and then soft again when swapping back because Sonos bar needs to be on 100% for me to utilize my Chromecast remote fully.
So for another test 
i actually for completely different reasons was able to swap from my LG 55 nano90 to LG 55 CX OLED. Both are the 2020 model.
Same problem...persist so either 1 it's a built in issue with 2020 motherboards and software (all updated) or it's just a setting I don't know how to change.
I would really prefer to use Chromecast remote but if I can't that will be okay...I don't think it's the remote. When I swap between high res and stereo constant i would like the audio to stay at "50%" and allow me to use same remote to go up and down in volume.