Its not just France, its an issue across northern/western Europe. Combine that with the difficulty of getting a proper AC installed in a rented house/apartment with normal stone walls and it explains the current lack of AC units. Most landlord will immediately be scared for the buildings substance. The few AC units that you see are those "mobile" devices with a single tube hanging out of a window. Even window units are a rare occasion because of the kind of windows installed across the country. Not to mention regulations stopping renters from changing the outer appearance of the house. I really dont see a viable plan to retrofit living spaces in a reasonable time frame. At this point i would even be doubtful, that there would be enough people capable of doing the job available.
An often overlooked point is also the situation in workplaces, some parts of Europe simply lack the worker protection needed during heatwaves.
I honestly dont see how most countries in Europe could retrofit buildings to a detectable degree, let alone finance it. There are just to many older buildings build for another kind of climate. Providing air conditioned shelters during the weeks of deadly heat sounds like the most realistic option. That would be similar to what is being done in winter to prevent people from freezing to death.
