I installed KDE on a Raspberry 4 PI. It is working quite well (with a reasonable performance) but audio support is sticking to always output on the analog output rather than using the digital output as required for HDMI output. Selecting the output on the Phonon Device Priority has no influence. Each newly started application will output it's audio on the analog output. Using the tool pavucontrol-qt will give an option to select the output for each application creating an output stream. Switching to the digital output in this tools directs the sound to the right output. STEPS TO REPRODUCE 1. Connect the RPI to a TV/Monitor with HDMI audio support. Leave the analog plug unconnected (to be sure) 2. Adjust in the Systemsettings the selected output to Digital Audio in the Multimedia->Device Priority tab. 3. If you try the Test button you should already observe that for the digital output option there is no sound. 4. Running any app (e.g. VLC) will also not provide any outputs. 5. In VLC one may override the audio device from the VLC menu. In general, for any streaming application the output can be overridden using the tool pavucontrol-qt 6. The output selection will remain active as long as the application is running. Re-starting or starting another application requires again to select the right output. OBSERVED RESULT There is no way to get any sound outputs from the connected monitor/TV EXPECTED RESULT The default audio port shall be configurable and selection shall be persistent. SOFTWARE/OS VERSIONS Linux/KDE Plasma: RaspberryPI OS aka Debian Buster (available in About System) KDE Plasma Version: 5.14.5 KDE Frameworks Version: 5.54.0 Qt Version: 5.11.3 ADDITIONAL INFORMATION RPI OS switched recently to make use of pulse audio. I remember that audio support also was not working well without it, but triggering output through the device settings made it somehow happen that audio was working. When playing around too much in the phonon settings there may be reported an error about broken Audio HW.
A workaround is to disable the analog Audio output in the settings. After this only a single output is available and this will then be selected as default from all applications, also from Desktop.