I tried the approach suggested by Torsten Bronger in How do I add lens correction for my model+lens to Lensfun in Darktable? (extracting the xml files from 0.3.0 tar and overwriting in /usr/share/lensfun). There are three problems: 1. Darktable still doesn't recognize the lens, even if the entry is in one of the xml files. 2. Darktable no longer shows a drop-down list of lenses (clicking in the box, nothing happens) but it did before I overwrote the files. 3. http://wilson.bronger.org/lensfun_coverage.html says that lens "Nikkor AF-S 18-55mm f/3.5-5.6G DX VR II" is available in 0.3.0, but the downloaded .xml files do not show an entry for it (only for VR without "II"). I tried duplicating the VR entry and adding "II" to the name, but still, Darktable wouldn't recognize it.
Darktable's exact wording for the lens is: "Nikon AF-S DX Nikkor 18-55mm f/2.5-5.6G VR II"
So my question is, how to manually install lensfun 0.3.0. The README is not clear on where to extract the files. Do I extract them into /usr/share/lensfun? or in a temp area and MAKE will correctly copy them to /usr/share/lensfun?