The Flatpak bundle doesn't include the gnome-control-center binary,
and the sandbox prevents it from accessing one that's part of the host
operating system or a different bundle. Therefore, it's not possible
to use g_app_info_create_from_commandline to launch the Online
Accounts panel when running as a Flatpak.
However, with a hole poked in the sandbox, it will be able to see the
org.gtk.Actions-based  D-Bus API offered by gnome-control-center
, which can be conveniently accessed through GApplication's remote
This will be used by the subsequent commit.
 gnome-control-center commit ab0576f1f00172c4