The instance of XFCE that I am using seems to be really buggy. I am forced to use both xfce-volumed-pulse and xfce-pulseaudio-plugin side by side, and the issue that arises from this is that now there are two notification indicators for the present volume.
When I remove xfce-volumed-pulse (this plugin is no longer shown on the official documentation), the multimedia key stops working, so there’s no notification indicator.
But when I remove xfce-pulseaudio-plugin, I am no longer able to access the slider widget in the control panel, that allows me to tap into pavucontrol.
What is happening here?
I don’t know what program really is catching the keys, but from my keyboard, the vol+/- mute speaker and mute mic are working, my behavior enable keyboard shortcut checkbox is rightly checked.