You can ‘group’ any Sonos speaker(s) with the Arc to send the TV audio to those speaker(s). There is a very slight audio delay, so I would personally choose to either mute the Arc audio, or set the Arc volume limiter to ‘0’ so the audio just plays on the grouped speaker(s) …that would eliminate the potential for any echo in the room caused by the slight delay.

A further and perhaps better option, is to set the TV output to PCM stereo and adjust the Arc’s ‘TV Dialog Sync’ slider bar in the room settings to bring the grouped audio playback (on all speakers) into alignment. Put the grouped speaker(s) on a 5Ghz WiFi connection too and all devices then play in sync with each other and provide near-perfect lip-sync stereo audio too with the video on screen.