lightroom-xmp-export

This Lightroom plugin will extend the XMP files written by Digikam with the data from the Lightroom database.

This is particularly useful to transfer metadata of video files, since Lightroom doesn't write XMP files for them.

The following metadata is supported:

keywords
city
province/state
location
country (the country code needs to be set in Lightroom though to be imported correctly in Digikam)

Author

in Digikam, enable the creation of XMP files: Preferences / Metadata / Sidecards / Write to sidecar files Enable "Read from sidecar files" Enable "Write to sidecar files" "Write to XMP sidecar for read-only items only" should be sufficient
in Digikam, make sure that all metadata gets exported: Preferences / Metadata / Behavior Check all checkboxes in "Write This Information to the Metadata"
in Digikam, add the tag "PLACEHOLDER_TAG" you want to add keywords from Lightroom to The PLACEHOLDER_TAG must be at the root of the tags
in Digikam, select the relevant files, and trigger: Item / Write Metadata to Selected Files That will write XMP sidecar files, even for videos
in Lightroom install the plugin XmpExport plugin using the Plugin Manager
in Lightroom, select the relevant files, and select in the menu: File / Plug-in Extras / XMP Export This will update the XMP sidecar files with the keywords from Lightroom The progress can be seen by running the following command in the Terminal: tail -f ~/Documents/XmpExport.log (Press CTRL-C to stop)
In Digikam, trigger Item / Read Metadata from Selected Files That will read the XMP files back into Digikam, with the information from Lightroom.