Issues include problems with running non Apple programs like Adobe Creative Cloud, some Microsoft Office products, hardware issues with mouse and keyboard conenctivity, and even instances of freezing up during install of the new OS. You don't need that picture of that big mosquito bite you got eight years ago so I'm deleting it). (PS, mom if you're reading this, you should consider not taking photos of every little thing you see. I've been remoting into my mom's computer to convert her millions of photos to jpegs and moving them onto an external drive so when Apple inevitable changes their photo browser file formats again, I won't have to ******************** deal with it. With Catalina, the issues have been really big, most notable, getting rid of iPhoto and iTunes. When MOuntian LIon came out, I remember having huge issues with running Microsoft programs (This was also the time Microsoft switched to subscription services) and I made the permanent switch to Pages and Numbers because of that. When iOS 4 came out, it crashed people's phoens a lot.
The OS on iPhones, iOS 13.1 had an issue where you could not use your keyboard at all. The same thing happens every time that Apple updates its OS.
