If you are unable or unwilling to upgrade your OS, the web remains your safest, most reliable channel to OneDrive.
If you already have a version installed, it might still function. If you need to reinstall, you must find a version released prior to September 2021. Recommended Version onedrive for macos 10.13.6
: Tools like rclone or odrive can sometimes bridge the gap by connecting to your OneDrive storage via alternative sync engines that may still support older macOS versions. Reset OneDrive - Microsoft Support If you are unable or unwilling to upgrade