All is good. Yay! I built the system in /usr/local/src running as root as hat’s how I’ve built most 3rd-party stuff over the years. Running the demo as an unprivileged user took a bit of tweaking with "chgrp -R pcl " and “chmod -R g+w” (I’m user pcl in group pcl) and the addition of symlinks to eups and loadLSST.bash from a working directory in ~pcl. There may be a more elegant way of doing this, or even a script to do it automagically, but I didn’t go looking for it. The step seemed to be needed because something wanted to write a temporary file in lsst_stack/stack/current/ups_db/. (An obvious question: is this wise? Should not /tmp or some other such temporary directory be used instead?)
After that the demo worked perfectly. I’m a happy bunny
Now to learn how to drive this stuff.
Once more, many thanks for your assistance and your patience in dealing with a clueless newbie.