Okay, found the extra parameter to add in CONFIG from the openacs 5 install docs for aolserver[1]. According to the wording on the "Unix-like system and supporting software" page[2], I thought tDOM was expected to be installed before continuing.. (glad to have found it!)
1. https://openacs.org/doc/openacs-5-0-0/aolserver4.html
2. https://openacs.org/doc/openacs-5-0-0/unix-installation.html
