No audio when source device is muted
According to the initial message, "This device can be muted, the audio will still be shared", however, when you "mute" the player (no matter if it's a browser, an application, or the system), the receiver stops playing. You can turn down the volume up to the minimum, that works, but it has to be greater than 0.
Tested in flatpak versions - Ubuntu 22.04