Vertico expands the minibuffer which I do not like.

You might want to try some Vertico extensions such as vertico-flat that displays completion candidates horizontally.

I see. Thanks for the explanation. It seems a long standing issue: https://github.com/Maato/volumeicon/issues/49

But the problem is that if you plug in a USB or bluetooth headset, it doesn’t automatically switch to it as the default.

How about module-switch-on-connect?

You may need gtk-murrine-engine (actual package name may differ).

** ‘minibuffer-allow-text-properties’ also affects completions. When it has a non-nil value, then completion functions like ‘completing-read’ don’t discard text properties from the returned completion candidate.

Thanks for the commit! It looks very handy when we pass propertized strings to completing-read.

For logging, PANEL_DEBUG=all (source) seems to work. Anyway, did you reboot the system after removing xfce-volumed-pulse (so only xvce-pulseaudio-plugin should be enabled) ?