Part of the problem with it is that most people aren't bothered by it, so people who are affected by it are sort of unintentionally gaslit by the people around them. In this case the user can simply choose to return it, but will have to realize what the cause of the issue is, determine whether changing the brightness can solve the issue, and if not return it within 14 days. Most of the reviewers aren't helping. I've seen several reviews and hardware tests and only one mentioned this issue.
I also want to know what the actual flicker frequency is. The Phawx said that the OLED screen on the Deck can go down to 45Hz, but my peripheral vision can see 60Hz Christmas lights flickering. But the 60Hz lights are easier to see because they follow half of an AC wave, starting dim then getting really bright for a moment then getting dim again, before turning off entirely for 1/120th of a second. Now that I think about it, there was one CRT monitor which I could discern flickering on, and it was a second monitor so I always saw it in my peripheral vision. That was annoying to use. I don't remember if it gave me a headache though.