This app needs to get ability to read/write host's GSettings, but there is no way to do that in Flatpak or Poral. So, the app gets the host's XDG_DATA_DIRS environment value with flatpak-spawn and bridges schemas directories under each directory in that value.
As discussed in https://github.com/flathub/flathub/pull/5266#discussion_r1606015669
This app needs to get ability to read/write host's GSettings, but there is no way to do that in Flatpak or Poral. So, the app gets the host's XDG_DATA_DIRS environment value with flatpak-spawn and bridges
schemasdirectories under each directory in that value.