If this is reproducible on stock Ubuntu 21.10, then this isn't only gtk4/xdg-desktop-portal-gnome that's broken, but gtk3/xdg-desktop-portal-gtk too.
If this is reproducible on stock Ubuntu 21.10, then this isn't only gtk4/xdg- desktop- portal- gnome that's broken, but gtk3/xdg- desktop- portal- gtk too.