Have not tried it but came across this some time ago. https://github.com/guysoft/FullPageOS

As long as you are connected, I think network adb will stay active but if you leave your network f.e., you have to re-enable it in the developer options. But don’t take my word for it. Feels like google changed this behaviour every major release with android.

Did you check out balenaSound by the way?

On their blog they say: This project is made possible by the awesome work of various open source projects, including Shairport Sync for Airplay, Raspotify for Spotify Connect and Snapcast for multi-room audio sync. So they “just” glue existing stuff together which leaves you with roughly the same limitations as if you would do it yourself. It might allow spotify to be used with snapcast for multiroom but as I’m a yt music user I didn’t digg any deeper.

fcast looks nice, but if I understand it correctly it would require implementation in every specific application

Correct. That’s what I meant with “adoption”. Really hope it finds adoption but I really doubt it :(

I have not yet found a solution I would be happy with because you always have to sacrifice on something. Your scrpcpy idea is neat and something I haven’t though off but:

1. others (visitors etc.) wouldn’t be able to “just use it”
2. it would drain the battery
3. on none-rooted devices the adb network connection is not permanent I think? either way, getting the connection is not as simple as “pressing a button to cast”

As it stands, I have given up on integrating mobile devices into my multiroom audio setup for many reasons. Right now I have my HTPC as the snapcast server and RPIs (soon to be old surface 4) as clients dotted around with a special script on the server-side to do some magic in regards to Kodi.

By chance I came across fcast which sounds interesting but relies heavily on adoption which you will not see in apps like youtube, youtube music, spotify etc. so (to me) it has no relevance.

Android App is just for controlling