I don't have the same device as you, but Search Your Settings for "Brightness" and you should see one of the Options as "Always On Display".
If you do, then you can change the Lockscreen Brightness here, either to "auto brightness", or slide the adjustment bar to what level of brightness you want.
Thanks a lot for the answer.
But doesn't that just change the brightness in general?
I don't have it on automatic (I can try it), but it's way down to the left at night. That's when the problem is. If I look at the lockscreen (no problem with the rest of the phone) at night, I can really feel the light in my eyes.
New to Samsung, had a Huawei phone before, where the brigthness was the same on the lock screen, and the rest of the phone.
Hi, if you have face recognition on please turn it off in settings.
You can change this in Settings >> Lock Screen and Security >> Face Recognition >> Brighten Screen >> Tap the switch on the right-hand side to turn on/off.