Receiving "To Play [song title] Stop Playing on Another Device" pop-up on Mac mini

I just got a Mac Mini M-4 Pro.

From the outset, every time I stopped playback on the Mini, then started& stopped using another device for playback, Music on the Mini would have two "To Play [song title] Stop Playing on Another Device" pop-ups.

I am the only user, and I'm not trying to use more than one device for playback. The pop-ups are simultaneously useless and annoying.

How can I make the bad thing stop?

[Re-Titled by Moderator]