[Note: the below is for Windows 11. In Windows 10 the interface might be a bit different.]
In Settings / Time & language / Language & region, I selected “Language options” from the … menu for English (United States).
Then for Text-to-speech I clicked on the “>” next to Installed. That brought up the Accessibility > Narrator page, with the option to “Add natural voices”. Clicking on the Add button brought up a dialog for English but also a link to “Choose a different language”.
Maybe if you explore this you might be able to install some additional natural voices for French. When I switched to French, I saw entries for Henri (Natural) and Denise (Natural) and installed them.
Edit: Hmm, never mind. The newly installed voices don’t show up in the {{tts-voices:}} listing.