I am glad that we were able to get Bluetooth audio playback working in Kubuntu as expected. To summarize, the steps we found to work are included below.
If the device has already been paired, it is recommended to do the following steps:
1. Left-click Bluetooth icon next to the clock and choose ‘Configure Bluetooth’
2. Click headset/audio device and choose ‘Remove’.
If the device has not been added yet, or was removed in the steps above, perform the following:
1. Put Bluetooth headset in pairing/discoverable mode according to the device’s instructions.
2. Click ‘Add Device…’ in the ‘Configure - KDE Control Module’ window.
3. Select the headset from the list of devices and choose ‘Next’.
4a. Accept ‘Connect to the Audio service’ and click ‘Finish’
4b. A KDE Workspace notification appears to inform that the Bluetooth device is connected and configured.
5. Right-click the sound icon next to the clock and choose ‘Audio Setup’
6a. In the ‘Device Preference’ tab, choose ‘Audio Playback’, then in the right pane, select the Bluetooth device and put it to the top of the priority list.
6b. Repeat raising priority for the remaining categories under ‘Audio Playback’. (Notifications, Music, Video, Communication, Games, Accessories)
7. Switch to the ‘Audio Hardware Setup’ tab.
8. In the ‘Sound Card’ drop-down menu, choose your Bluetooth audio device.
9. In the ‘Profile’ drop-down menu, choose ‘High Fidelity Playback (A2DP)’ if available, otherwise use ‘Telephony Duplex (HSP/HFP)’.
10. Click ‘Apply’ in the lower-left corner of the ‘Audio and Video Settings - KDE Control Module’ window.
11. Use the buttons under ‘Speaker Placement and Testing’ to validate that sound is being produced. If no sound is emitted, use the volume control on your Bluetooth audio device to raise the volume in addition to raising the volume by left-clicking the audio icon next to the clock, choosing ‘Mixer’, and adjusting the slider for your device upward.
12. Test audio playback from an application. (Before testing, you may want to restart the application if it was already open.)
After completing these steps, all audio should route to the Bluetooth audio device.