I have been having same issue with the S10+ . Eye strain and headaches. Currently I am testing an app from Google play which I found today called OLED Saver which completely disables PWM ( flickering of AMOLED screen). Let me know if it works for you.
Have you decided that this worked for you? I have been having SERIOUS eye strain since I got the S10 in April. I thought I was crazy to think it could be the phone's fault--I went to the eye doctor a few days ago trying to figure it out. I don't want to go through the hassle of buying a new phone but if this app doesn't work, I may have to!