Try the latest update once it becomes available to your system from the play store 

Firstly, the music service (iBroadcast) has to support the alpha index. Last I checked, it did not, only Apple Music do.

Next, the app has to see the index and render some UX under it. This is only available in the Sonos Desktop apps.

The very latest mobile app has the UX only wired to the local library index, not the music service index.

To my knowledge there exists only one mobile app that *may* be able to give you what you need. It’s on Android. And I wrote it (see my profile). I am away from home so cannot verify it works with iBroadcast. As iBroadcast don’t support the alpha index and my app can’t read it, its not as optimal as it could be, but I believe it should work.

iBroadcast does support alpha index. My songs are loaded from iBroadcast alphabetically into the Sonos Controller App queue on my android phone. I just wish the queue in the mobile app had a scroll bar like in the Sonos Controller App for desktop.

Oh sorry you are talking about the Queue - the alpha index doesn’t matter in that case.

Is there really no scroll bar on the queue on Android? My app at least has one of those.

​@Hrdnox 

As advised, update your app with last week’s update which added A-Z scrolling. The facility might not immediately appear even once your app is updated as it’s rolling out gradually, but you do need the latest app version to get it.
It’s also vital to run the system update too, as well as the latest app.

Did the update. Still no scroll bar. I'll keep checking to see when it appears.