I also have this bug, Dell Latitude 7390, kernel upgraded to 4.15.0-99-generic about 2 days ago, couldn't get the sound (internal laptop speakers and audio jack) to work. However, HDMI sound through external monitors worked.
I'd be happy to run some diagnosis with the old & new kernels if that'd be helpful.
I also have this bug, Dell Latitude 7390, kernel upgraded to 4.15.0-99-generic about 2 days ago, couldn't get the sound (internal laptop speakers and audio jack) to work. However, HDMI sound through external monitors worked.
I'd be happy to run some diagnosis with the old & new kernels if that'd be helpful.