Useful tools include `dbus-monitor` to watch requests being made,
and `dbus-send` and the similar `busctl call` for manual dbus calls.
You can test the integration with the [portal-test](https://github.com/matthiasclasen/portal-test) flatpak app.
Alternatively you can trigger it with [trigger-screen-shot.py](https://gitlab.gnome.org/snippets/814) and [xdp-screen-cast.py](https://gitlab.gnome.org/snippets/19).