Samsung
Turn Camera and Screen Flash Notifications On or Off auf Samsung
Flash notification uses the camera LED or a full-screen flash to signal incoming calls, messages and app alerts, independent from the small notification LED on the front of some Samsung models. It sits inside the accessibility tools because it was originally built for users who cannot rely on sound or vibration alone.
If the feature stopped working, it is almost always because the toggle was switched off, either during a reset or a system update. You find both switches in the same place: Settings ➔ Accessibility ➔ Advanced settings ➔ Flash notification. From there you can turn Camera flash notification and Screen flash notification on or off independently.
Camera flash notification fires the rear LED, which is useful when the phone lies face down or across the room. Screen flash notification lights up the display itself and works better at night or when the camera lens is covered.
Keep in mind that flash notification does not respect silent or Do Not Disturb profiles unless you configure that separately, and it triggers for every app that sends a notification, not just calls and messages.