I wanted to change the audio output in the new Podcasts.app in Catalina from my MacBook (nmbp) to my HomePod (mmhp). Can you guess where you have to click to achieve that? Correct, you need to click the checkbox in the mmhp line. Nothing else in the UI is clickable. And they don’t behave like checkboxes, they behave like radio buttons, i.e. only one can be active at a time. So… how do you set the audio output to multiple targets, a primary feature of AirPlay 2? Well, you don’t.