Microsoft acknowledges this incompatibility. In official community responses, they state that "new installations on unsupported operating systems will be blocked" and recommend using "OneDrive on the web as a workaround". For users with paid subscriptions, this is often an unsatisfying response.
Once you've installed and signed in to the OneDrive app, you can start using it to store, access, and share your files. Here are some key features: onedrive for macos 10.13.6