Adding to the informal data: today the lines appeared on my beloved M1 iMac (July 2021) - so, more than four years before the problem occurred, but still very annoying. It's been used for hours every day, though not for anything very demanding, and rarely with the brightness much over 50%, I'd say.
Off to Apple tomorrow... fortunately I still have the extended Apple Care on it, so I hope the repair will be covered - and not take too long.
Off to Apple tomorrow... fortunately I still have the extended Apple Care on it, so I hope the repair will be covered - and not take too long.