Ha!!

My friend was using zoom today in xfce4 (all trees just as setup by installer, transformed and updated with the latests 66, both root and user trees) and suddenly the desktop froze, video picture stood still, mouse kbd all frozen, but audio continued to work.
I sshed and killed zoom for starters, and she had pulled her camera off.
Through ssh the system seemed fine.
zoom killing didn't affect anything ... still frozen at 10:23:39-42

Xorg.0.log shows this errrors:

[    22.716] (**) Option "xkb_options" "grp:alt_shift_toggle"
[    22.717] (II) event7  - Dell WMI hotkeys: is tagged by udev as: Keyboard
[    22.717] (II) event7  - Dell WMI hotkeys: device is a keyboard
[    22.718] (II) config/udev: Adding input device PC Speaker (/dev/input/event6)
[    22.718] (II) No input driver specified, ignoring this device.
[    22.718] (II) This device may have been added with another device file.
[   177.275] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 18ms, your system is too slow
[   178.276] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 34ms, your system is too slow
[   178.947] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 17ms, your system is too slow
[   199.037] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 20ms, your system is too slow
[   301.051] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 16ms, your system is too slow
[   302.436] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 25ms, your system is too slow
[   302.803] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 25ms, your system is too slow
[   303.285] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 11ms, your system is too slow
[   305.871] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 12ms, your system is too slow
[   305.871] (EE) event2  - PixArt USB Optical Mouse: WARNING: log rate limit exceeded (5 msgs per 60s). Discarding future messages.
[   435.347] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 21ms, your system is too slow
[   480.202] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 18ms, your system is too slow
[   490.318] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 13ms, your system is too slow
[   491.337] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 15ms, your system is too slow
[   494.358] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 12ms, your system is too slow
[   494.358] (EE) event2  - PixArt USB Optical Mouse: WARNING: log rate limit exceeded (5 msgs per 60s). Discarding future messages.
[   499.561] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 15ms, your system is too slow
[   513.576] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 13ms, your system is too slow
[   515.227] (II) event2  - PixArt USB Optical Mouse: SYN_DROPPED event - some input events have been lost.
[   516.940] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 17ms, your system is too slow
[   517.856] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 13ms, your system is too slow
[   519.646] (EE) event2  - PixArt USB Optical Mouse: client bug: event processing lagging behind by 19ms, your system is too slow
[   519.646] (EE) event2  - PixArt USB Optical Mouse: WARNING: log rate limit exceeded (5 msgs per 60s). Discarding future messages.

Logs from 66

# 66-inservice -p13 consolekit
Name                  : consolekit
Version               : 0.2.0
In tree               : boot-user
Status                : enabled, up (pid 695) 9368 seconds
Type                  : longrun
Description           : consolekit daemon
Source                : /usr/lib/66/service/consolekit
Live                  : /run/66/tree/0/boot-user/servicedirs/consolekit
Dependencies          : consolekit-log
External dependencies : dbus:root
Optional dependencies : None
Start script          : 	execl-toc -d ${dir_run}
                        	execl-cmdline -s { console-kit-daemon ${cmd_args} } 
Stop script           :  s6-rmrf ${dir_run} 
Environment source    : /etc/66/conf/consolekit/0.2.0
Environment file      : cmd_args=!--no-daemon
                        dir_run=!/run/ConsoleKit
Log name              : consolekit-log
Log destination       : /var/log/66/consolekit
Log file              : 
2020-11-13 22:03:09.189828180  console-kit-daemon[690]: WARNING: failed to run script: Failed to execute child process “/usr/bin/pm-is-supported” (No such file or directory)
2020-11-13 22:03:09.191796942  console-kit-daemon[690]: WARNING: failed to run script: Failed to execute child process “/usr/bin/pm-is-supported” (No such file or directory)
2020-11-14 10:23:14.926521280  missing action
2020-11-14 10:23:14.926580123  
2020-11-14 10:23:21.915998796  console-kit-daemon[695]: WARNING: failed to run script: Failed to execute child process “/usr/bin/pm-is-supported” (No such file or directory)
2020-11-14 10:23:21.917255822  console-kit-daemon[695]: WARNING: failed to run script: Failed to execute child process “/usr/bin/pm-is-supported” (No such file or directory)
2020-11-14 10:23:21.918401945  console-kit-daemon[695]: WARNING: failed to run script: Failed to execute child process “/usr/bin/pm-is-supported” (No such file or directory)
2020-11-14 10:23:39.671639171  console-kit-daemon[695]: WARNING: failed to run script: Failed to execute child process “/usr/bin/pm-is-supported” (No such file or directory)
2020-11-14 10:23:39.672932258  console-kit-daemon[695]: WARNING: failed to run script: Failed to execute child process “/usr/bin/pm-is-supported” (No such file or directory)
2020-11-14 10:23:39.812669137  console-kit-daemon[695]: WARNING: failed to run script: Failed to execute child process “/usr/bin/pm-is-supported” (No such file or directory)
2020-11-14 10:23:39.816417079  console-kit-daemon[695]: WARNING: failed to run script: Failed to execute child process “/usr/bin/pm-is-supported” (No such file or directory)
2020-11-14 10:23:39.819800971  console-kit-daemon[695]: WARNING: failed to run script: Failed to execute child process “/usr/bin/pm-is-supported” (No such file or directory)

Log destination       : /var/log/66/dbus
Log file              : 
2020-11-13 13:02:02.225887960  dbus-daemon[620]: [system] Activating service name='org.freedesktop.Accounts' requested by ':1.24' (uid=1000 pid=1180 comm="xfdesktop --display :0.0 --sm-client-id 27c69e4d9-") (using servicehelper)
2020-11-13 13:02:02.352702377  dbus-daemon[620]: [system] Successfully activated service 'org.freedesktop.Accounts'
2020-11-14 10:23:14.702921079  dbus-daemon[627]: [system] Activating service name='org.freedesktop.PolicyKit1' requested by ':1.0' (uid=0 pid=695 comm="console-kit-daemon --no-daemon ") (using servicehelper)
2020-11-14 10:23:15.319720041  dbus-daemon[627]: [system] Activating service name='org.freedesktop.ColorManager' requested by ':1.1' (uid=0 pid=596 comm="cupsd -f ") (using servicehelper)
2020-11-14 10:23:16.050108478  dbus-daemon[627]: [system] Successfully activated service 'org.freedesktop.ColorManager'
2020-11-14 10:23:17.817978359  dbus-daemon[627]: [system] Successfully activated service 'org.freedesktop.PolicyKit1'
2020-11-14 10:23:39.231184987  dbus-daemon[627]: [system] Activating service name='org.freedesktop.UPower' requested by ':1.22' (uid=1000 pid=1194 comm="xfce4-power-manager --restart --sm-client-id 2dc7f") (using servicehelper)
2020-11-14 10:23:39.517303918  
2020-11-14 10:23:39.517316379  (upowerd:1211): UPower-Linux-WARNING **: 10:23:39.514: Could not acquire inhibitor lock: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.freedesktop.login1 was not provided by any .service files
2020-11-14 10:23:39.652953090  dbus-daemon[627]: [system] Successfully activated service 'org.freedesktop.UPower'
2020-11-14 10:23:42.000815710  dbus-daemon[627]: [system] Activating service name='org.freedesktop.Accounts' requested by ':1.24' (uid=1000 pid=1186 comm="xfdesktop --display :0.0 --sm-client-id 27c69e4d9-") (using servicehelper)
2020-11-14 10:23:42.136008164  dbus-daemon[627]: [system] Successfully activated service 'org.freedesktop.Accounts'

% 66-inservice 
~/.66/log/dbus-session@ xxx
Log file              : 
2020-11-14 10:23:33.810451172  dbus-daemon[907]: Activating service name='org.a11y.atspi.Registry' requested by ':1.0' (uid=1000 pid=813 comm="xfce4-session ")
2020-11-14 10:23:33.861438820  dbus-daemon[907]: Successfully activated service 'org.a11y.atspi.Registry'
2020-11-14 10:23:33.864014273  SpiRegistry daemon is running with well-known name - org.a11y.atspi.Registry
2020-11-14 10:23:38.628675356  dbus-daemon[878]: [session uid=1000 pid=878] Activating service name='org.freedesktop.thumbnails.Thumbnailer1' requested by ':1.71' (uid=1000 pid=1186 comm="xfdesktop --display :0.0 --sm-client-id 27c69e4d9-")
2020-11-14 10:23:40.971875198  
2020-11-14 10:23:40.971883709  (tumblerd:1191): tumbler-WARNING **: 10:23:40.969: Failed to load plugin "tumbler-raw-thumbnailer.so": libopenrawgnome.so.8: cannot open shared object file: No such file or directory
2020-11-14 10:23:41.658194355  
2020-11-14 10:23:41.658202115  (tumblerd:1191): tumbler-WARNING **: 10:23:41.658: Failed to load plugin "tumbler-odf-thumbnailer.so": libgsf-1.so.114: cannot open shared object file: No such file or directory
2020-11-14 10:23:41.716556381  Registered thumbnailer /usr/bin/gdk-pixbuf-thumbnailer -s %s %u %o
2020-11-14 10:23:41.720700088  Registered thumbnailer ffmpegthumbnailer -i %i -o %o -s %s -f
2020-11-14 10:23:41.730774158  Registered thumbnailer /usr/bin/gdk-pixbuf-thumbnailer -s %s %u %o
2020-11-14 10:23:41.751576906  dbus-daemon[878]: [session uid=1000 pid=878] Successfully activated service 'org.freedesktop.thumbnails.Thumbnailer1'

From search I think it relates to xfce4 session and power manager that is trying to execute this logind script

Edit:
66-stop/start sddm and it is alive and well - no reboot to test if it happens again. I told her to proceed as nothing happened to see if it happens twice in the same session.

Some xfce4/freedesktop/logind/pm upower bug I suppose ...

Never happened to me, never seen on Obarun before, never never never....
There is a 1st for everything.