M2 Max Mac studio with Sonos Arc Soundbar Setup.

I’m using an Apple Studio M2 Max and a Sonos Arc without any sub or surrounds, connected to an LG TV through HDMI eArc. 

I need help setting up MacOS’s “Audio Midi Setup” program.

Currently I use the format: 6ch 24 bit integer 48.0 kHz and have the speakers configured as 5.1

if I choose 8ch 24 bit integer 48.0 kHz I can configure the speakers as Atmos 5.1.2

but when I try to apply this, I get an “Overlapping Channels” error.

I've also noticed that the format changes back to 2 ch stereo by itself.

Does anyone know what setting I should be using in Audio MIDI Setup for the best sound?