I recently installed Ubuntu 16.04. I come from Windows 10 where everything worked fine (front/read jacks and headphones).
Now on Ubuntu, if I connect the headphones in the back, I get no sound at all. I tried
sudo alsamixer force-reload without success.
I connected the headphones in the front and the sound is working, but in the sound settings at
Play sound through, there is no device and i cannot control sound volume and stuff like that.
Now with a second pair of headphones I tried the front and rear jacks at the same time and the sound comes through the rear jack and in the sound settings at Play sound through it appears Line-Out (build in audio) and if I disconnect the front headphones then I got no sound in the back.
In alsamixer everything appears to be fine. Nothing is muted.