Works like a charm with my Raspberry Pi, but only once you get it set up properly.
May take some time and effort to sort out the connection though, especially if you have not allowed the app access to your location…
The app requires location data to enable you to jump into the WiFi selection. The WiFi connection in turn is required to set up Volumio for the first time on Raspberry Pi.
During my initial attempts to get it running I denied the app access to location data (thought it didn’t need it). It got into an endless loop of trying to find Volumio devices, which it couldn’t actually search for since it had no WiFi access…