Automatically saving categories into IPTC tag

[falconxn]

I'm looking for a solution for my company that would allow us to maintain a database of tagged images. XnView MP seems to have a very convenient UI to select the tags (categories), but I couldn't figure out how to set it up so that the category information is automatically saved as an IPTC tag.

By checking the Metadata/IPTC&XMP/"Export DB category to XMP subject and IPTC keyword" toggle, it seems like categories are saved as XMP tags, but not as IPTC data. Unfortunately for long-term compatibility XMP is not acceptable, because even XnView can't interpret this format, let alone other image management software.

Did I overlook some hidden setting that would enable this functionality? I hope that is the case, because the other alternative is to keep using digiKam, which is violently unstable

[xnview]

Your picture files have already IPTC data?

[falconxn]

No, they do not have IPTC. They just come out of a camera (or iPhone) without any processing.

[xnview]

No, they do not have IPTC. They just come out of a camera (or iPhone) without any processing.

Please sned me a sample file?