I bought a Radex Lupin by Quarta and measured pulsation of almost every light source and display in my environment.
My iPhone Xr showed about 1-1.5% pulsation while iPhone 13 pro max about 10% the best with up to 60% at low brightness. iPhone 12 Pro Max has about 20% pulsation at 100% brightness up to 100% pulsation at low brightness levels. Surprisingly, 13 mini has the lowest pulsation at lower brightness - about 30% which is too high anyway.
I bought iPhone 12 Pro Max and exchanged display to Chinese IPS display from Incell in the nearest unofficial service. Incell has PWM - about 3.3% pulsation at about 300Hz. The display itself is good enough though it doesn't support True Tone. I feel some difference with Xr. I think that most part of that is due to the True Tone and a bit from PWM because a do not feel stress on eyes but have some feeling in the brain.
The solution is not perfect but it's something that is usable and doesn't hurt my eyes so far. I'll update if something comes out.