Here is How to Fix Samsung Galaxy Note 10 Plus Adaptive brightness randomly turns off.
1. Open Settings
2. Go to Apps
3. Tap on Device Health Services
4. Open Storage
5. At bottom side tap Manage Storage
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6. Tap on Reset Adaptive Brightness, This will ask for a confirmation, click OK
7. Click on Clear Data, This will ask for a confirmation, click OK
8. Restart your device (Not mandatory)