Created attachment 164890 [details]
Screenshots of normal/working XMP tags and non-working/Ultra HDR tags

STEPS TO REPRODUCE
1. Take a photo with Android (14+) camera with "Ultra HDR" enabled (I used Pixel 6a). The "Ultra HDR" setting is found in the camera advanced settings (https://piunikaweb.com/2023/12/08/how-to-enable-or-disable-ultra-hdr-in-the-pixel-camera-app/)
2. Make sure Digikam is configured to write face tags metadata (under Settings > Behavior)
2. Import the photo into Digikam and scan for faces (or manually add a face)
3. Specify a person's name to trigger Digikam to write metadata.

OBSERVED RESULT
No face metadata is found in the XMP section. Neither Microsoft Photo or Metadata Working Groups Regions tags are present. The only thing it writes is person's name as a "keyword" under IPTC

EXPECTED RESULT
Both Microsoft Photo and Metadata Working Groups Regions should be present.

SOFTWARE/OS VERSIONS
Windows: 10

ADDITIONAL INFORMATION
When inspecting XMP tags for "Ultra HDR" images, various "Container" tags are present. These seem to be documented at https://developer.android.com/media/platform/hdr-image-format#GContainer_details 
I suspect somehow they're preventing Digikam from writing face data to XMP.
This issue is preventing other applications that rely on XMP from reading face tags