Run siri commands in a shortcut, connect to airplay
Today, on iOS 12.2 it’s not possible to select the output of music from the shortcuts app, so you’re not going to be able to automate that via tap or via Siri shortcut.



The good news is if you already are using AirPlay - the shortcut to play something leaves that alone, so you could automate playing something else to the current sound output destination for music.

This function is so awesome, that I bought a HomePod so I could have Siri play music I can hear. That way my AppleTV and iOS devices can output sound there as well as it being the Siri that listens to what I want to hear.