Glenn, I do run RT from a portable drive. It gets started by using a script that I’ve written that intends to set normal Windows environment variables to also reference the portable drive. I’ve never set the variable named ALLUSERSPROFILE but I could.
While that is interesting I’m afraid it doesn’t completely explain the behavior I’m seeing. Using original lensfun folder finds lots of cameras and lenses just NOT some that have been added to the mil-canon.xml file. While the complete new set of xml files extracted from .zip file finds nothing.
Something else I’ve now noticed is that the folder I downloaded as .zip file (i.e., contains what looks like all of the files in the lensfun folder) contains a pair of files named “lensfun-database.dtd” and “lensfun-database.xds” that are NOT present in original lensfun folder.