Cast any audio from Android to Pi Musicbox

Hi all,
I’ve been using the musicbox with IOS devices over airplay. No dedicated players needed. Now we have an Android device in the family. How can I cast music from spotify or youtube to the musicbox WITHOUT having to invoke dedicated players? All I want is to see the little arrow underneath the audio stream that lets me select the desired output?
Thank you for helping.

I don’t know what this means, is this icon on your ios player? Or your android music player? Google cast doesn’t support ‘any audio’, Android has nothing like that. And even for those Android apps that support Casting, the Google Cast receiver software that would run on pimusicbox doesn’t exist. I don’t think there is a solution for you.