Apple has released iOS 13.4 which focuses on bug fixes.
Most notably, they address a problem caused by iOS/iPadOS 13.4 wherein users running that version could not join FaceTime calls with users running older versions of iOS or macOS—iOS 9.3.6 or OS X 10.11.6 or earlier, to be specific.
Users began reporting the issue shortly after iOS 13.4 launched, and the timing was unfortunate given that users have been seeking digital ways to connect with family and friends amidst shelter-in-place orders across the world. Apple claims this issue is now fixed.
iOS 13.4.1 additionally fixed a bug that prevented the Bluetooth option in the quick-actions menu on the homescreen from working. The iPad version of the update also fixes an issue with the flashlight on recent iPad Pro models.
You can download the update by opening Settings > General > Software Update.
