Watched a bunch of DNA testing videos including this one
https://www.youtube.com/watch?v=SPZ8SCKwUSwOur French protagonist is first disappointed that his first DNA map doesn't show France itself but only neighbour countries.
But ouf! the 2nd DNA analysis company shows a big "French or German" blob.
Meanwhile the CNRS guy says "well these companies collect DNA from a bunch of people and record it with the test subject's claimed ethnicity in order to build their database."
Meanwhile the CNIL guy says "well DNA analysis is illegal in France unless ordered by a judge or a doctor."
My logical conclusion (I don't think it is explicitly enunciated in the video):
either the DNA companies don't have any data from actual French people that live in France, or they obtained said data illegally, or from a handful of French people that live outside France.
And they hide this weakness of their database from their customers.
So either they can't tell or they don't want to tell whether your DNA matches a specific region of France unless it can be bundled with a neighbour country (Breton/Celtic, Iberic, Basque, Italian, German) or a historical invasion (Norse, German) or migration (Roma, Jewish) etc.
So don't expect Auvergnat vs Breton vs Normand vs Corse details anytime soon... (assuming it would even be technically possible. But I remember a documentary about Etruscan features that survive in today's local population in that particular area of Italy, so...)
Edit: actually Breton vs Corsican will probably show in a roundabout way, as one would be bundled with Welsh/Scottish/Irish, and the other one with Italian. But Auvergnat vs Alsacien?
Future me already did it.