It's not just S20 users who are experiencing this. The Galaxy S10 Lite is also suffering from the green screen. This happens when the brightness is set to automatic and reduced. The part that is usually gray turns green. Black remains black, but gray turns green.
The black is black because the pixel is turned off but in gray there is no problem. I have Android 10 and less than 15 days with August Security Patch.
This problem can be corrected with an update, but Samsung needs to be aware that it also affects this version and not just the S20.