Complex JSON queries

I have many images with xmp sidecar metadata. DAM I am using is DigiKam for the keyword tagging however, all software that supports cataloging is very limited in terms of querying metadata. This includes Lightroom and Capture One. For example, lets say I have many images, some have 1 person and other 2 - 5 people. Now, I want to assign metadata per person in an image. To do it in DigiKam, Lightroom or Capture One I would either need to create neste