Xubuntu 18.10 problem with dual-monitor dual-desktop configuration.

[Jeffery Small]

   I have a system that has been running fine for years under all past
   versions of Xubuntu up through 18.04.  The dual monitors are configures
   *without* Xinerama so that separate desktop sessions with separate
   panels launch on each screen.

   After the recent upgrade to Xubuntu 18.10, even though it is properly
   configured, the second monitor is not being recognized.

   However, the second monitor is actually active:
   - Upon boot it goes from black to a uniform grey  (although, it is back
      to black after trying to start a second window manager)

      - The mouse can travel onto the second screen (pointer visible) and
      keyboard input (e.g., volume keys) are active
      - Xscreensaver displays on both monitors when it goes active
      - In a terminal window, issuing the command:   *DISPLAY=:0.1
      xfce4-terminal*   displays the new terminal on the grey background of
      the second screen

   I have tried to manually start an *xfwm4* window manager, *xfdesktop*
   desktop and *xfce4-panel* panel on the second screen, with no success.
   I have also tried to create a $HOME/.xinitrc file with the desired command
   but this also fails.

   I have provided a page at the following link with very detailed images
   and notes on configuration, log files, command output, etc. so as not to
   clutter up this post

   http://smallthoughts.com/xfce/xfce.html

   So my questions are:
   - What changed between Xubuntu 18.04 and 18.10 that is keeping the OS
      from detecting the second screen and configuring it properly and
what can I
      do to rectify the problem?
      - Supporting dual monitors with separate window managers seems like a
      common set-up, yet I can't find straightforward documentation on enabling
      this. Am I missing something?
      - What modifications do I need to implement to get this second screen
      and desktop configuration re-enabled?

   Thanks for any help you can offer.

Regards,
-- 
Jeff
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