I cannot find definitive documentation that discusses what devices support Portrait Upside Down and which ones do not.
I know that the "X" series do not by design
seems iPad works just fine (all size/versions)
but not any of the iPhones :(
supposedly something do to with FaceID
FYI... the pList contains all the keys for all orientations for both iPhone and iPad, and the default of allbutupsidedown has been changed to all