Hi lameohh1,
Thanks for posting in Apple Support Communities.
When you use HomePod as a speaker, you would need to use it with another HomePod to create an audio pair. It would not work with other AirPlay compatible speakers. This is currently not supported.You can setup home theater audio using the steps below.
Set up home theater audio
1. Assign your Apple TV and HomePod or HomePod mini to the same room in the Home app. If you want to use two HomePod or two HomePod mini 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.
3. Select Use as TV Speakers to turn on home theater audio.

These steps are found in Set up home theater audio with HomePod or HomePod mini and Apple TV 4K - Apple Support.
Regards.