When playing music on HomePod and AppleTV if I start playing a show on the AppleTV it replaces the audio on HomePod

1. Open Settings  on Apple TV.
2. Go to Video and Audio, select Audio Output, then select an option

If you have An Apple TV 4 or 4K you can swipe down from the Siri remote , choose Audio, then drag down to select or deselect.

OR you can long press the TV/Home button to bring up control Center and choose the Airplay icon to switch the output

Additionally if you want a show Or Music to play through homepod and would like to use the remote to control volume deselect the TV Audio to off

Out of curiosity, how did you insert the Settings icon? Is this apart of SF Symbols? I have noticed Apple has done this with a lot of their support documents.

Hello,

You would need to deselect the HomePod as an audio destination on Apple TV before you can independently play audio on your HomePod.