Est-il possible de remplacer un clavier QWERTY type UK par un AZERTY?

If you just bought the system you may want to return it and get the system with the keyboard you want.

As far as switching the keyboard out, yet its possible by replacing the uppercase assembly. But at this point the part is not available.

For reference here’s the 2018/19 15” butterfly version MacBook Pro 15" Top Case/Bat/TP/UK - Silver - $885 USD. Which will be at least the late fall before any will be available. Replacing the keycaps might be possible we just don’t know if they will be available and if this is something you can do or not. I can tell you I won’t even try the butterfly keyboard as its so very easy to break the caps and the key mechanism.

So that leaves us with the last option of using a skin which has the UK keyboard layout. That is what I would do as being the cheapest and leaves the keyboard intact.