Public bug reported:

Setup: two external screens connected through separate DP ports and a
docking station to a laptop Lenovo T480

When the laptop is launched in the docking station (lid is closed) the screens 
remain off (there is information about missing signal).
When the laptop is launched out of docking station (using only the internal 
screen), after logging to the Gnome session, connecting to the docking station: 
there is an image on two external screens. However, once the laptop is 
suspended or screensaver enabled (switch off all screens), after wakeup, all 
screens remain off.

This bug is 4.15.0-44 kernel specific. With the previous version
4.15.0-43 the external screens were served properly.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-4.15.0-44-generic 4.15.0-44.47
ProcVersionSignature: Ubuntu 4.15.0-43.46-generic 4.15.18
Uname: Linux 4.15.0-43-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
AudioDevicesInUse:
 USER        PID ACCESS COMMAND
 /dev/snd/controlC1:  afiergol   9976 F.... pulseaudio
 /dev/snd/pcmC0D0p:   afiergol   9976 F...m pulseaudio
 /dev/snd/controlC0:  afiergol   9976 F.... pulseaudio
CurrentDesktop: GNOME
Date: Wed Jan 30 17:27:50 2019
HibernationDevice: RESUME=UUID=7b4a9d17-f6d7-42ed-8f12-34f46c41cc6c
InstallationDate: Installed on 2018-04-05 (300 days ago)
InstallationMedia: Ubuntu 16.04.4 LTS "Xenial Xerus" - Release amd64 (20180228)
MachineType: LENOVO 20L6S04200
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.15.0-43-generic 
root=/dev/mapper/ubuntu--vg-root ro quiet splash nogpumanager 
intel_iommu=on,igfx_off iommu=pt kvm.ignore_msrs=1
RelatedPackageVersions:
 linux-restricted-modules-4.15.0-43-generic N/A
 linux-backports-modules-4.15.0-43-generic  N/A
 linux-firmware                             1.173.3
SourcePackage: linux
UpgradeStatus: Upgraded to bionic on 2018-08-22 (161 days ago)
dmi.bios.date: 11/07/2018
dmi.bios.vendor: LENOVO
dmi.bios.version: N24ET44W (1.19 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20L6S04200
dmi.board.vendor: LENOVO
dmi.board.version: Not Defined
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.modalias: 
dmi:bvnLENOVO:bvrN24ET44W(1.19):bd11/07/2018:svnLENOVO:pn20L6S04200:pvrThinkPadT480:rvnLENOVO:rn20L6S04200:rvrNotDefined:cvnLENOVO:ct10:cvrNone:
dmi.product.family: ThinkPad T480
dmi.product.name: 20L6S04200
dmi.product.version: ThinkPad T480
dmi.sys.vendor: LENOVO

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: Confirmed


** Tags: amd64 apport-bug bionic

** Summary changed:

- Lenovo T480: problem with externals screens
+ Lenovo T480: problem with external screens

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https://bugs.launchpad.net/bugs/1813956

Title:
  Lenovo T480: problem with external screens

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