Source: meta-kde Version: 5:102 Flatpak recommends xdg-desktop-portal-gtk | xdg-desktop-portal-backend
xdg-desktop-portal-backend is a virtual package provided by the GTK and KDE backends. Since there is a KDE backend, I think one of the KDE metapackage should go ahead and install it by default so that a user who installs Flatpak will get the correct KDE integration without needing to take the further action of finding and installing the KDE backend. For reference, the kubuntu-desktop and kubuntu-full metapackages recommend xdg-desktop-portal-kde. By the way, Snap will soon be using xdg-desktop-portal too. Thanks, Jeremy Bicha