Bought a Google Pixel 3a and it is the best phone for ages now.
Had an iPhone 6 Plus before which caused strain immediately. I seem to have issues with Apple products in general. Apple TV dithers a lot as well and caused strain. Only iPhone which seems ok in the store is an iPhone 8 plus.
The Pixel 3a (not the 3) uses an Oled screen which caused a bit strain for one day but everything good now.
Have not seen any better phone in stores yet.
Edit: It is running Android 10, the one in the store also had Android 10. Comes with 9, but not sure if this was worse for the eyes.