At Apple it is now good manners to maintain two iOS versions: The current version has been updated to 13.5, the previous version, which still runs on an extremely large number of devices, is now 12.4.7, which essentially closes security gaps, including the Mail App.
iOS 13.5 also comes with an interface for COVID-19 tracing. The API, which Apple has developed together with Google, allows apps to use the Bluetooth function of smartphones to trace which people have come close to each other and to notify them in case of an infection. For iOS 12, this functionality is not available.
In addition, on an iPhone with Face ID, the PIN code can now be entered more quickly, as people often wear a mask, which makes Face ID useless. So it is of course quite pleasant to be able to enter the numerical code quickly.