Black screen on Kubuntu 22 LXD container

I'm running Kubuntu 22.04 in an LXD container.

When I connect using x2go, KDE starts up (I see the splash screen) but 
then the screen goes black with a cursor. After a short time, the lock 
screen is shown, with password field, so I think that x2go is working. 
When I log in, the screen goes black.  There is a cursor, but neither 
left nor right clicks have any effect.

Something similar happens running tightvnc-server:  I can open a remote 
window using vncviewer but it is all gray and unresponsive.

In both x2go and vnc windows, I can bring up a terminal window using 
alt-F2 to display krunner and then running konsole. When I look at 
environment symbols, I see the following:

XDG_SESSION_TYPE=tty
XDG_CURRENT_DESKTOP=KDE

SDDM appears to be running, as does plasma_session.

Anyone have any suggestions?


-- 
Michael Eager