I loved the screen on my 2011 iMac and replaced it with a 2020 model this weekend, but found that the fonts were blurred and the screen is headachy after a couple of minutes' use. Apple help desk advised me to upgrade to Big Sur and I fiddled with 'font smoothing', accessibility options etc etc for ages but still found it impossible to work on comfortably. Not sure what the difference is between this and my 2011 Mac - maybe retina display? And thoughts grateful received.