Before removing a memory card, it must be logged off or deactivated from the Samsung device. If the memory card is not ejected by the system, data may be lost. Software problems on the Samsung device cannot be ruled out.

Disabling the memory card will disconnect all connections and accesses between the device and the card, after which the memory card can be removed from the Samsung device.

Android 10 (One UI 2.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Device care
Step 3:  Tap on  Storage
Step 4:  Tap on  Advanced
Step 5:  Tap on  Unmount
  1. Open the Settings
  2. Tap on Device care
  3. Tap on Storage
  4. Tap on Advanced
  5. Tap on Unmount

Samsung Instructions