Hello,
I have the same problem. When I upgraded my Ubuntu 18.04.05 LTS system
from Kernel linux-image-5.4.0-53-generic to linux-image-5.4.0-56-generic
my second screen was not detected.
The output of "sudo lshw -c video" had *display-unclaimed" similar to
the output below.
*-display UNCLAIMED
description: VGA compatible controller
product: Kabini [Radeon HD 8400 / R3 Series]
vendor: Advanced Micro Devices, Inc. [AMD/ATI]
physical id: 1
bus info: pci@0000:00:01.0
version: 00
width: 64 bits
clock: 33MHz
The next output is from "sudo lshw -c video" after I reverted to Kernel
linux-image-5.4.0-53-generic.
sudo lshw -c video
*-display
description: VGA compatible controller
product: Kaveri [Radeon R7 Graphics]
vendor: Advanced Micro Devices, Inc. [AMD/ATI]
physical id: 1
bus info: pci@0000:00:01.0
version: 00
width: 64 bits
clock: 33MHz
capabilities: pm pciexpress msi vga_controller bus_master cap_list rom
configuration: driver=amdgpu latency=0
resources: irq:49 memory:b0000000-bfffffff memory:d0000000-d07fffff
ioport:f000(size=256) memory:feb00000-feb3ffff memory:feb40000-feb5ffff
*-display
description: VGA compatible controller
product: Oland XT [Radeon HD 8670 / R7 250/350]
vendor: Advanced Micro Devices, Inc. [AMD/ATI]
physical id: 0
bus info: pci@0000:01:00.0
version: 00
width: 64 bits
clock: 33MHz
capabilities: pm pciexpress msi vga_controller bus_master cap_list rom
configuration: driver=amdgpu latency=0
resources: irq:52 memory:c0000000-cfffffff memory:fea00000-fea3ffff
ioport:e000(size=256) memory:fea40000-fea5ffff
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https://bugs.launchpad.net/bugs/1906452
Title:
5.4.0-56: External Display not recognized
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