Airplay
Where do I find my Airplay password using macOS Mojave? How do I update that password?
MacBook Pro 15", macOS 10.14
See Change settings for HomePod - Apple Support. Typically you would configure AirPlay to allow connections from anyone on the same wireless network without needing a password, but you can set and edit one if required.
See also If you can't use AirPlay or mirror your device's screen - Apple Support.
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