A Microsoft file hosting and synchronization service.
Hello, Maarten Vennemann
Welcome to Microsoft Community.
We are aware of the issue and are working on resolving it. The url files will automatically convert back to folders when the issue is resolved. For now, we recommend accessing shared folders that are in this state on OneDrive.com.
Please refer to this information here:
Add and sync shared folders to OneDrive for home - Microsoft Support
Best regards,
Chandy.L | Microsoft Community Support Specialist