Hi Phil,
Unfortunately the French IGN maps are no longer available. There used to be a server that Gaia could hit, which users asked us to link in the app.
That server is now unavailable. We looked into acquiring a license for the IGN maps, to re-sell in Gaia GPS, but we don’t consider it a priority right now.
I suggest trying out the OpenHikingMap if you are interested in an alternative.
If you are interested, you can request the addition of IGN maps to our Idea Forum. You can subscribe to email notifications so you'll know when other users vote or comment on your idea, or if we move forward with it into production.
Regards,
Ashli Baldwin
User Support