Today apple officially released iOS 13.4.1/iPadOS 13.4.1, less than two weeks after the previous iOS 13.4, and from the version upgrade, the system should be just for some Bug fixes.This update solved a problem,That is, devices running IOS 13.4 cannot make FaceTime calls with devices running IOS 9.3.6 and earlier or OS X El Capitan 10.11.6 and earlier. It also fixes an error in the setup application that may cause a failure when selecting Bluetooth features from the quick action menu on the home screen.
Shortly after the release of IOS 13.4 and Mac OS 10.15.4, FaceTime problems were discovered, which made it impossible for iPhones, iPads and Macs running these updates to make or receive FaceTime calls from old devices that could not be upgraded, such as iPad 2, 3rd generation iPad, iPhone 4S, 1st generation ipad Mini and 5th generation iPod touch.
Here are the full release notes for iOS 13.4.1 updates:
IOS 13.4.1 includes bug fixes for iPhone.
Fixed a problem where devices running IOS 13.4 could not participate in FaceTime calls with devices running IOS 9.3.6 and earlier or OS X El Capitan 10.11.6 and earlier.
The iPad OS 13.4.1 update fixes the same two issues, but solves a third error, which could cause the new 11 and 12.9 inch iPad Pro models' flashlights to fail to turn on after the flashlight button in the control center or the flashlight button in the lock screen is clicked.
From the current point of time, IOS 13.4.1 may be the last update of IOS 13 operating system, because Apple is ready to transition to IOS 14.