We are currently at point where we need any support for native messaging in xdg-desktop-portal and currently carry over xdg-native-messaging-proxy from sewick@redhat.com . We either need to update to the latest version (recently released 0.1.0) or go with the original portal implementation. This would ideally follow upstream decision to diverse as less as possible, which also applies for Firefox, where we also ideally avoid custom downstream patches for our builds.