This may need a bit of adjustment for kms users, as vc4 becomes the sound driver which switches to digital audio and has different device names. But I like the names, so I hope it works out.
Edit:
When using kms, the sink name changes to:
alsa_output.platform-fef00700.hdmi.iec958-stereo
If you run:
$ pacmd 'update-sink-proplist alsa_output.platform-fef00700.hdmi.iec958-stereo device.description="HDMI"'
It does set the description to: device.description = "HDMI"
However, the Plasma widget does not reflect that setting, it continues to be called:
Digital Output (S/PDIF)
When using fkms, the widget does change to reflect the setting using the bcm2835 sink.
Edit 2:
This same behavior occurs with Plasma on both Raspberry Pi OS and Arch.
Edit 3:
When using kms
$ pacmd list-sinks
ports:
iec958-stereo-output: Digital Output (S/PDIF) (priority 0, latency offset 0 usec, available: unknown)
So I assume this is what the widget uses for a description.
Edit 4:
The S/PDIF is the headphone jack, yet the sink is hdmi. The widget only has the S/PDIF output device. Yet my actual audio-out is hdmi, no headphone output. A bit wonky.
With fkms, the widget has both a hdmi and a headphone analog audio-out.
Edit 5:
If you manage to get both Headphones and Digitial Output with kms working, the following works:
pacmd 'update-sink-proplist alsa_output.platform-bcm2835_audio.stereo-fallback device.description="Analog"'
pacmd 'update-sink-proplist alsa_output.platform-fef00700.hdmi.iec958-stereo device.description="HDMI"'