When I plug in my usb headphones the system recognizes them - however, the audio doesn’t switch to the headphones; it continues to be sent to the speakers. I can go into phonon to set defer the internal audio below the headphones but still doesn’t change the audio stream to the headphones. If I select headphones under phonon, the audio when eventually transfer to the headphones.
In addition, when I disconnect the headphones, the audio will not switch back to the internal speakers.
This worked flawlessly under 12.1. I never had to manually select which device to use.