Podcasts: can't select Airplay speaker

Note - I can select Airplay speakers in the MUSIC app, and can select Airplay speakers systemwide (in the command center or sound control panel, but these aren't ideal because ALL audio - including calls and meetings - then routes through my Sonos).

Problem - in the PODCASTS app (macOS), when I click on the Airplay icon (next to the (i) info icon), nothing happens. It's dark and remains dark.

No list of speakers. Cannot change audio (sound) output.

I seem to recall this was a problem with older macOS, but thought it was fixed by now.