On Debian 11, I always have my speakers and heaphones plugged in. When selecting sound devices, for the Line Out Built-in Audio, I get the sound in the speakers as expected. For the Heaphones Built-in Audio option, I get the sound on both, the speakers and the heaphones! In
alsamixer, Auto-Mute is disabled, since otherwise I was not getting any sound from the speakers when the headphones were plugged in.
How can I get the system to only play the audio from the headphones when both, the speakers are plugged into the rear panel of my computer, and the headphones are plugged to the front panel?