Samsung Smart Switch for Windows

Go to Device Manager → Uninstall the “Samsung Mobile USB Composite Device” → Reconnect phone. Also try disabling USB Selective Suspend in Power Options.

Unlike older phones, the Galaxy S21 Ultra does not require traditional “USB drivers” for basic file transfer (MTP) on modern Windows 10/11. Windows installs generic drivers automatically.

Samsung Developers → USB Drivers

Avoid tools like Driver Booster or Driver Easy for Samsung drivers—they often install wrong or outdated versions. Stick to Samsung official sources.