I'm using Amarok 2.9.70 on Opensuse Leap 15.2.

Before the updates today, this Amarok can be heard from my bluetooth headphone. But now, it can only be heard from wired headphone. I tried to refresh the Amarok using YaST and also reinstalled the phonon backends. The strange thing is that my Mplayer can be heard from both wired and bluetooth headphones.

What did I do wrong?

Amarok uses what the system provides, there is nothing in our code that selects any specific audio output. You need to look at the audio settings of your system directly.

I solved it!

The problem is the phononsettings. It should have the VLC backend. This backend requires all libraries with phonon-vlc names to be installed. Once all installed, the device listed will have pulseaudio sounds server. It works like a charm.