HomePod Mini - HDMI Arc question

See Use HDMI ARC or eARC with your Apple TV 4K (2nd generation) - Apple Support. The article suggests that what you want to do is possible. I would assume the Apple TV 4K (2nd gen.) needs to be turned on for this to work, but you can test that.

tt2

Hi Evurenno,

You can setup and use home theater audio with your HomePod mini by completing the steps listed here: Set up home theater audio with HomePod mini or HomePod and Apple TV 4K that are also below.

"Set up home theater audio

1. Assign your Apple TV and HomePod mini or HomePod to the same room in the Home app. If you want to use two HomePod mini or two HomePod speakers, create a stereo pair, then assign the stereo pair to the same room as your Apple TV in the Home app.
2. Turn on your Apple TV. You'll be asked if you want to Use HomePod speakers as Apple TV speakers. Select Use as Apple TV Speakers to turn on home theater audio. "

Best regards.