
You cannot edit files directly from the OneDrive app, you have to use the Office mobile app for that. And in order to edit files in the Office app, you need a valid/qualifying Office 365 subscription: https://support.microsoft.com/en-us/office/what-you-can-do-in-the-office-apps-on-mobile-devices-with-a-microsoft-365-subscription-9ef8b63a-05fd-4f9c-bac5-29da046833ea