Re MapboxGL: see https://github.com/rinigus/pure-maps....PureMaps.json , mapboxgl qt version part. You would have to install mapbox-gl-native-qt and mapbox-gl-qml, as shown in that flatpak JSON recipe. Well, except install location. Use my repos and it should all work. Its way easier to work on desktop - even with Jolla making a decent job to simplify development.
Re OSM Scout Server packaging: I am now writing up a doc for deb-based repos and will probably compose flatpak as well for it. Although, flatpak does impose few limitations, as far as I can see - no systemd socket activation and dbus name is predefined.
Good luck with the talk!