@userPQrldhjBOt Light manager is a third-party app and would only appear if you have downloaded this app. To determine which app is causing an issue with your phone, it would be recommended to start with the most recently installed app. Uninstall the apps until you find the one causing the issue.
You can test the phone in Safe Mode to determine if it is a third-party app causing the problem.
If the issue persists, it is recommended to have the phone evaluated by a certified technician. You can locate an authorized service location using this link: https://www.ubreakifix.com/samsung
Yes ,I too had same problem for my s9+ ,I too tried all what you had done ...crying like anything.. cache partition also done ..what to do now,didn't tell simply to walk me to nearest service Center and pay 40$ in service Center please..