As of now there is no central listing of safe laptops (PWM wise) However I know of Clevo/Sager gaming laptops, it may indeed be possible to swap out the screen for a 20Khz PWM panel from AUO (none of this stuff is 100% confirmed, and I'm not dropping $1500 on a laptop just to have it flicker) 😛 Maybe another time.
I have a friend who works in R&D for Apple in California and he got me in contact with the head of displays for Apple. The jist of it is that 2015 MacBook Pro 15inch use no PWM until 50% brightness, at which point they use a 100Khz PWM frequency, which is well above the migraine threshold and is "undetectable" to most tests (even some cheap oscilloscopes) I probably will be able to go to the Apple Store soon and give the various displays there a PWM test using my Canon T5i and may also go to a local store (NCIX) and Best Buy soon as well to give various laptops the PWM test (can't spend too long to avoid migraine from overhead lights)
Some Russian guy made a PWM detecting device using a "photosensor" that hooks up to an Android phone, plots the PWM frequency and is able to just be passively held in front of the monitor. I am researching how to build this technology for myself so I can use it and possibly sell some units cheaply 🙂 Stay tuned for that