Similarly to Headphone jack not working?, I have a Dell XPS 13 and since I upgraded to Ubuntu 16.04, my headphones jack is not working anymore, while internal speakers work fine. when I plug in headphones I do not see any window that asks me whether it's microphone or headset like it used to.
I tried every solution on the mentioned link and none worked (even after reboot or sudo alsa force-reload): - modifying analog-output-headphones.conf in /usr/share/pulseaudio/alsa-mixer/paths/ - modifying /etc/modprobe.d/alsa-base.conf
I tried updating linux kernel to 4.6 but it didn't work as well.
It seems I'm not the only one who face this as I saw in comments on the mentioned link + Headphones is not working in 15.04 Dell XPS 13