A Microsoft file hosting and synchronization service.
Dear Jens,
Good day! Thank you for posting your query in our community.
Based on your description, Search feature doesn't work properly in OneDrive for iOS.
Since the problem happens on the latest version of OneDrive app as well, I am afraid that the problem may be related to the backend. Given this situation, more resources need to be involved on the issue in your environment. I suggest you contact the administrator in your company if you aren’t the administrator and follow the steps in the article to open a ticket, because support team there will have specific diagnostic tools that can help troubleshoot this issue further, and their support will continue to investigate this issue and provide suggestions for you.
Appreciate your understanding.
Sincerely,
Jazlyn | Microsoft Community Moderator