A safer approach is to update the Lensfun database in your user profile instead of overwriting /usr/share/lensfun.

What worked for community members:

1. Create a local Lensfun database folder: mkdir -p ~/.local/share/lensfun

2. Download and extract the updated database there: cd ~/.local/share/lensfun wget http://wilson.bronger.org/db/version_0.tar.bz2 bunzip2 version_0.tar.bz2 tar xvf version_0.tar

If Darktable still fails to load lenses after copying newer XML files, the issue may be XML format compatibility. Older Darktable/Lensfun versions may not understand newer database files, especially if the root tag is lensdatabase version="1". In that case, a matching Lensfun version may need to be built and installed, or the XML format adjusted to what your installed Lensfun expects.

If you compile Lensfun from source, extract it to a normal directory first, then run cmake, make, and make install; don’t just copy files into /usr/share/lensfun manually.

In short: use ~/.local/share/lensfun for database updates, and avoid mixing a new database with an older Lensfun library unless the XML format is compatible.