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I get the additional layer of backup, but remember you are riding 700km in Italy/France, not doing a month-long expedition into Tibet. Just saying, worst case you turn back down the hill and get back to the last house/village you rode by.
If you really want a map though, search for hiking maps of the most remote areas, have a look here: https://www.escursionista.it/categorie/cartografia/carta-escursionistica.html?mode=list#limit=25&mode=list®ioni_italia=7132
That would be the Italian Geographic Military Institute I'd say: https://www.igmi.org/en/Home?set_language=en and here is where you can browse the maps https://www.igmi.org/en/geoprodotti#b_start=0
Good luck navigating the website.
Personally I would use maps.me app, never let me down,