@Hui Wang
No pop-dialogue. When headphone plug-in, it switched to headphone from speakers automatically. It can be confirmed in PulseAudio Control Panel. In 18.04 it work without any problem.
@CarpalCarpal
I have KDE and Xfce4 desktop environment on my system, both of them have the problem , so I don't think the problem is relative to desktop environment. Maybe I can try Ubuntu Desktop.
@Hui Wang
No pop-dialogue. When headphone plug-in, it switched to headphone from speakers automatically. It can be confirmed in PulseAudio Control Panel. In 18.04 it work without any problem.
@CarpalCarpal
I have KDE and Xfce4 desktop environment on my system, both of them have the problem , so I don't think the problem is relative to desktop environment. Maybe I can try Ubuntu Desktop.