Public bug reported:
1. Problem DOES appear on Lenovo T470s (Intel).
2. Problem DOES appear on Lenovo T14 Gen2 (AMD).
3. Problem does NOT appear on either of the above *when in the Live Installer*.
I specifically checked that my dock behaved well under the Live
Installer before deciding to move
EDIT: Updated title.
Taking the dock out of the loop and simply plugging in an HDMI monitor
also causes the problem. Below is the syslog from single plug/unplug
cycle.
```
$ tail -f /var/log/syslog
Apr 26 18:54:49 dathon systemd[1]: Starting Hostname Service...
Apr 26 18:54:49 dathon
This is a DisplayPort-related issue. At the office, I was able able to
try out an HDMI-only dock. The problem did NOT occur, and everything
worked perfectly.
Back at home, I switched my personal dock from DisplayPort to HDMI by
changing out the cables and, thus, using the dock's HDMI ports
@Daniel
(1) It's not possible to do a soft reboot under the error mode because
the displays are frozen. Will a hard power-off get the job done?
(2) Using "Ubuntu on Xorg" changed the symptoms somewhat, but the
outcome is still the same: the secondary monitor never cycles up -- it
stays black.
Same errors in my syslog. See full text of
https://bugs.launchpad.net/ubuntu/+source/gnome-
shell/+bug/1970495/comments/2
Relevant snippet:
```
Apr 26 18:57:17 dathon gnome-shell[1649]:
meta_monitor_manager_get_logical_monitor_from_number: assertion '(unsigned int)
number < g_list_length
I *did* see those messages when I was initially debugging the problem.
This is from dmesg in one of the logs I made:
```
[ 20.525519] amdgpu :07:00.0: [drm] *ERROR* mstb f21f0a30 port 1:
DPCD read on addr 0x4b0 for 1 bytes NAKed
[ 20.570355] amdgpu :07:00.0: [drm] *ERROR*
