I had installed digiKam from Flathub instead of system repository, and it had no access to any directories except ~/Pictures and /media. Is it properly?
This was solved in a simple way. I allowed access to “All user files” and Photo directory via Flatseal (equally:
flatpak override org.kde.digikam --filesystem='/way/to/photodirectory' --user). I think, it may confuse new users. GIMP, Darktable and other has
--filesystem=host by default.
Sorry for my English.
You should file an issue there.