One message is in English on game, but all other are in French. it's on transport madness scenarios, on the beginning.

I have look on crowin and the translation is present since 21 November (there https://crowdin.com/translate/factorio/23/en-fr)
On thursday.cube wrote:Thanks for the report.
This was caused by not updating the locale from crowdin before releasing the scenario pack, the string will be present in the next scenario pack update (today, most probably).