Peter, that was very helpful with respect to downloading. I was able to do the downloads using both methods.
However, when I substitute what I think is the applicable xml (obtained via first suggestion), in this case named mil-canon.xml, there seems to be no change in what I’m able to select in RT. In that, my new camera is NOT listed even though there is an entry for it in the xml file.
Then, using the zip file I extract the db folder (which seems to have the same files that appear in the folder named lensfun under RT) into the folder named share where the lensfun folder is located. After that I rename the original lensfun folder to a different name and rename the folder named db to lensfun. After that I start RT but when I go to “Manual Selected” under “Profiled Lens Correction” I’m unable to display anything under either “Cameras” or “Lens”.
What should I do now?