This has been discussed ad-nauseaum, but the answer is still pretty much the same: it's around 1 to 2 percent a day on 'big battery' flagships or the front screen on flips, and 3% on flip's full screen IF you don't action the notifications or keep tapping on the screen to wake it up/increase brightness. Since all these are OLED screens, power is very efficient on these tiny elements since most of the screen is effectively turned off.
Most of the time this 'loss' of power is pretty much offset by how much it saves you from actually turning on the screen to check on notifications (that is, again, unless you do power on the screen every time you get a notification anyway).