Looks like I failed to disclose that I do my photo processing on Windows rather than Linux.
However, something I’ve now learned about is that the complete Lensfun package includes code that can be used to periodically update the database in addition to converting lcp files for use in Lensfun databases. Given that new lenses constantly come into being the idea of constantly updating the database makes a lot sense, at least, from the packager’s point of view. I’m also aware that Lensfun has both a Version 1 and a Version 2. If the databases are different one might expect that both versions are NOT receiving all of the updates. Is it possible that Version 1 which seems to be what both Darktable & Rawtherapee are using is NO longer being updated?
I found another post on this forum from someone in a pretty similar situation to mine who would also like to run Lensfun on Windows. The answer was pretty specialized back in Jan 2021 which makes me think reliability could be at issue. This causes me to ask is Lensfun better positioned to run on Windows than it was back then?