second monitor suddenly not detected (resend)

[Karl Auer]

[I didn't see this appear in the mailing list. My apologies to anyone
who sees it twice]

This is a new one on me. For no apparent reason, the display manager
(Wayland/Ubuntu on 20.04) exited. I still had a console, so I logged in
and powered off the laptop gracefully.

Upon powering up, Ubuntu did not detect my second HDMI-connected
monitor. There are a couple of other niggles, such as a Gnome shell
extension having vanished. And the gnome tweaks tool doesn't show 90%
of the tweaks it used to. But the display looks OK otherwise.

I've looked for answers in google, but the answers don't seem to apply
(and are almost all regarding 18.04). I tried switching from Ubuntu to
Gnome and back at login, no change. Tried update/upgrade and it
upgraded a surprising number of packages in including Nvidia libraries
and suchlike, but no change. Ran "sudo dpkg-reconfigure gdm3", no
output and no change.

Short of re-installing Ubuntu, is it possible to reinstall or
reconfigure the graphics subsystem? This is a Lenovo Y540 with Nvidia
graphics hardware, and currently the nouveau driver is active.

Regards, K.

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Karl Auer (kauer at biplane.com.au)
http://www.biplane.com.au/kauer

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