iPad Pro 12.9” never can get LCD again at this point and most people would dismiss your issue entirely. Your only bet is Apple releasing a 240hz or 360hz OLED or something To mitigate the issue.
It’s a shame apple cares nothing about people with PWM sensitivities.
If the 19 KHz (19,000 Hz) Mini-LED already causes PWM-related eyestrain/headaches, I don't see how 240-360 Hz OLED would work any better.