Unknown display + no sound on upgrading kernel to 4.18 (Ubuntu 18.04)

Question

I am running a Dell Optiplex 7060 with Ubuntu 18.04 (dual-booted with Windows). The system only has Intel's iGPU (UHD Graphics 630) to which I have two monitors connected, and it uses the Realtek ALC3234 audio controller.

Both monitors and the sound were working without issue with the kernel 4.15.0-54-generic until I decided to update to kernel version 4.18 for work reasons. I installed the packages linux-image-4.15.0-25-generic and linux-modules-4.15.0-25-generic.

Now, whenever I log into Ubuntu with the kernel 4.18, the second monitor does not work, and the settings shows "Unknown display". Further, there is no audio, only showing the Dummy Output.

I have tried booting into the older kernel (4.15) and everything still works. Unlike this thread, there are no errors in dmesg. The kernel option nomodeset has no effect. I have tried deleting ~/.config/monitors.xml.

For the audio issue,

$ lspci | grep -i audio
00:1f.3 Audio device: Intel Corporation Cannon Lake PCH cAVS (rev 10)

None of these steps have had any effect towards fixing this problem. Interestingly, I had experienced this same problem when I had Ubuntu 16.04 installed on this system (a year back).

ubuntu-drivers devices does not show any devices requiring special drivers.

Any idea what could be happening here?

Answer 1

The problem was solved by installing the following packages:

• linux-modules-extra-4.18.0-25-generic
• linux-image-generic-hwe-18.04
• linux-headers-4.18.0-25
• linux-headers-4.18.0-25-generic
• linux-headers-generic-hwe-18.04
• linux-generic-hwe-18.04

The extra headers obviously didn't help, so it is one of linux-modules-extra, linux-image-generic-hwe or linux-generic-hwe.

Both linux-image-generic-hwe and linux-generic-hwe only have a changelog and a copyright notice. Source. The fix, therefore, must be from one of the modules shipped with linux-modules-extra.

The LTSEnablementStack/HardwareEnablement(HWE) packages seem to be really responsible.