I switched back to Android from Apple specifically for the LED Notification light that repeatedly blinks. Only to order this phone to find out their "LED Notification" is exactly what Apple uses - either the flashlight goes off once, or the screen flashes - WHAT.A.WASTE. And I can't even return this phone. It's useless to me. Even using apps doesn't work because I have to have the Always On Display turned on and the brightness all the way up and then I'm stuck staring at the clock on the screen. May as well sell this junk on ebay and go back to apple.
Led me know does require AOD on, but you can use a black wallpaper, you don't need the brightness up or the clock.
It can also be set to keep the notifications until dismissed.
There are several apps now that will use the camera LED on the front screen to display notifications. Some are free and some cost a few bucks.
As @pool_shark mentioned, LED Me is a good option and setup instructions are in this video. Also instructions for using Edge Lighting which is another option.