I am in Ubuntu 18.04.01 LTS with lowlatency kernel. Before I installed JACK, everything worked fine, both audio jack and built-in laptop's speakers.
After I installed JACK, the audio jack worked fine while I plugged my earphone in. But when I do not plug the output things through audio jack there is no sound anymore from built-in speakers.
I am using Cadence for configuring JACK. I also use PulseAudio. The image below shows my JACK settings. In Input/Output device, i choose my laptop's default audio card.
Your solutions will be appreciated.