I observed something interesting this week...
Way back in the late 1930's, when commercially viable discharge lighting came on the market, the magnetic ballast produced flicker at twice the mains frequency. Over the years, different mechanisms were used to mitigate the effect (lead-lag, distribution over three phases) until the electronic ballasts came on the market in the later years of last century. The high frequency made for virtually flicker free operation.
Now, cue in the advent of LED lights, the cheap hardware store ones have very annoying visible flicker. This week, I paid a visit to the electrical supplier. All their fluorescent troffers have been switched over to LED edge lit panels. I walked in and there was no apparent flicker. When I was waiting for service at the counter, I spotted one of those retro-style fans, that have metal blades and a metal enclosure. It was running and the blades had that slow movement appearance that is usually a tell-tale sign of flicker. I was kind of surprised that the LED panels produced flicker akin to magnetically ballasted fluorescent.