Hi @phatcher.

Thanks for reaching out and welcome to the community! Let me see what I can do to help you.

To better understand, may I know why you want to keep it on HDMI 1? 

ARC and eARC are protocols responsible for sending audio over an HDMI cable to home theater sound systems like Sonos Arc.

Sonos Arc must be connected to HDMI ARC or HDMI eARC to play any Dolby Atmos content.

To use voice assistant (Alexa and Google Assistant), Arc must be connected to your TV’s HDMI-ARC or HDMI-eARC input and your TV needs to have HDMI-CEC enabled.

ARC (Audio Return Channel) is the HDMI feature that allows Sonos to receive an audio signal from the TV over HDMI. Some TVs that support ARC have a menu setting to enable or disable it.

With TV CEC ‘enabled’ it lets Sonos take over audio playback from the TV's built-in speakers and control the volume. 

To enable or disable ARC and CEC  on LG TVs:

Enable ARC: Sound menu→ Select Audio Out (Optical/HDMI ARC). → Turn on Simplink

On some older LG TVs: Sound menu→ Turn on ARC Mode. → Turn off TV Speakers.

NOTE: On some TVs, you may need to select External Audio (Optical/HDMI).

Enable CEC: Home Button on remote → Settings → Simplink → Enable   

OR
Home Button on remote → Input Methods → Green Button for Simplink → Enable

Let me know how that goes.

Sorry for the delay responding. Thank you for your response.

I should clarify the Arc is putting out sound as expected.

My cable box is connected to HDMI 1 and then Arc is connected to HDMI 2 which is the arc connection for LG. When turning the TV on, the TV will show for a couple of seconds and then flips over to HDMI 2 and shows this image.  I have to press the input button to get back to HDMI 1