A family of Microsoft products that enable users to capture, organize, and reuse notes electronically.
Dear respected,
Good day! Welcome to Microsoft Community.
We went through your post carefully and do understand the situation that OneNote is showing in French while you have made sure the language settings have all been changed to English. In this situation, it seems like this issue happened on many users' sides, please refer to: OneNote 2019, changing the display language - Microsoft Community
Hence, we would like to suggest you try the resolution suggested in above thread(mostly about keyboard) and see if any of them can work for you:
Appreciate your understanding that sometimes the initial reply may not resolve the situation very soon. However, we can work together to narrow down and resolve the situation. Please kindly post back and provide the more information, then we can focus on your specific scenario and provide specific suggestions.
We'll be here for you to wait for your updates. I appreciate your time and effort on checking these above and thank you for your patience and cooperation. I hope that you are keeping safe and well!
Sincerely,
Mia | Microsoft Community Moderator