Music set to airplay to HomePod but playing on Mac

When I start my Mac, open Music, and play something, it will play on my Mac despite it is set to airplay to my HomePod and a Belkin device. I have to unselect and reselect them to get Music to start airplaying. Music remembers the settings but doesn't apply them between restarts.

In the screenshot, "Mac mini van Eric" is the device on which I am using Music. "SoundForm" is my Belkin AirPlay device and "Werkkamer" is my HomePod. Music remembers these settings from the last time I used it. When I play music, however, it plays on the Mac and not on these devices.

[Edited by Moderator]