The iOS and iPadOS 13.4.1 updates are available on all eligible devices over-the-air in the Settings app. To access the updates, go to Settings > General > Software Update.
The update addresses an issue that prevented devices running iOS 13.4 from participating in FaceTime calls with devices running iOS 9.3.6 and earlier or OS X El Capitan 10.11.6 and earlier. It also fixes a bug in the settings app that could cause choosing Bluetooth from the quick actions menu on the Home screen to fail.
Discovered shortly after the release of iOS 13.4 and macOS 10.15.4, the FaceTime issue prevented iPhones, iPads, and MAcs running these updates from making or receiving FaceTime calls from older devices that aren’t able to upgrade, such as the iPad 2, third-generation iPad, iPhone 4S, the first-generation iPad mini, and the fifth-generation iPod touch.
It wasn’t clear if the problem was caused by a bug or was intentional, but the fix included in today’s update clarifies that Apple did not mean to remove the option for devices running iOS 13.4 to communicate with older devices.
iOS 13.4.1 could be one of the last updates to the iOS 13 operating system as Apple prepares to transition work to iOS 14. There will be at least one additional update, though, as Apple is already beta testing iOS 13.4.5.