Do the French make their own hardware? An encryption app is useless if you don't 100% trust the hardware. Tainted hardware could figure out, log and send your keystrokes from screen taps/swipes all from silicon.
This is better that it was before. More security is better. Perfect security does not and cannot realistically exist for a complex system.
I do think have a reproducible binary would be a huge win. Even if you can't verify the integrity of a single build you could verify that build by consensus.
But France does have some domestic defence capability here - Thales make hardware security modules and similar products, and STMicroelectronics has chip design expertise while being partly state-owned.
Apparently, though, people whose threat model isn't dialed up to 11 don't deserve security or privacy?