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Best way to embed face tags in photos
(feddit.uk)
I don't think there is a way to add this to the EXIF data, so you will need some sort of external database to store it.
darktable used xmp, and that looks like an alternate metadata format, it looks like exiftools might be able to work with the xmp standard, and it looks like there's some face tagging features in xmp.
https://photo.stackexchange.com/questions/106410/how-does-xmp-define-the-face-region
Hosting your own services. Preferably at home and on low-power or shared hardware.
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