Re-installing a saved Joomla site on a newly loaded ubuntu system, the Akeeba Kickstart pre-analysis indicated that XML Support is required but missing from my system. I could find no place in the Kickstart documentation or on this forum to explain what XML Support is or how to install it.
After a lot of Google searches, I finally determined that XML support is an optional feature of PHP.
On ubuntu, all I needed to do was:
and then restart the apache2 service.
Hopefully, this post will provide others a more direct path to the solution.