Hello Jacques,
Thank you for posting in Microsoft Community.
Based on the description, there is issue with the language shows in Microsoft Loop desktop application. Let us see on what we can do to help address your concern.
Before we proceed any further, we would like to set your proper expectation that Microsoft Loop is still in public preview and users may experience known and new issues. During this preview, we will need your feedback to help us improve your experience.
To change the language of the Microsoft Loop desktop app, you can follow these steps:
- Open the Microsoft Loop app on your desktop.
- Click on the three dots in the top right corner of the app.
- Select "Settings" from the drop-down menu.
- In the Settings menu, click on "General" in the left-hand menu.
- Under "Language", select your preferred language from the drop-down menu.
- Close and reopen the Microsoft Loop app for the changes to take effect.
If your preferred language is not available in the drop-down menu, you may need to install the language pack for that language on your computer.
If the above steps does not works, please provide your experience as feedback to our developers. They'd love to hear from you about what's working well, what's not, and any ideas for improvements, including possible new features and functions. Your contribution will help us improve the user experience for you and all users around the world.
During this preview we want to hear from you to help improve your experience – so send us your feedback in the app to help us shape the journey.
In the bottom right corner, select Help> Give feedback.

On Android or iOS, tap your profile picture at the top left to find Help and feedback.
Link: Get started with Microsoft Loop - Microsoft Support
Regards,
Prince R
Microsoft Moderator