Now, running Evolution remotely from Jack2 is fast, but running
Evolution from Jack1 is slow and I get a message about
Xlib: extension "RENDER" missing
so I assume this is part of the problem, but I don't know if it's the
X11 server on Jack1 (or Wizard?) or something in my ssh setup. (Or
something else?)
Any ideas on how I can get Jack1 to see and use (or make available)
the RENDER option?
That looks like a difference in your sshd configurations or possibly
a PATH or other environment setting for user "mark". Note that you
were logged into both Jack1 and Jack2 as "mknecht" when you did the
xdpyinfo commands, and you're going into them as user "mark" via the
ssh connections.