Today, Apple has released a minor update for iOS 13, with iOS 13.4.1 which aims to fix a recent bug with FaceTime. iOS 13.4 was released before this update, about two weeks ago. iOS 13.4 came with iCloud Folder Sharing as well as cursor and trackpad support for iPad with iPadOS 13.4.
A bug was discovered recently for FaceTime where users running iOS 13.4 were unable to video call users on iOS 9.3.6 and earlier as well as those on OS X El Capitan 10.11.6 and earlier. Devices running iOS versions this old are the iPad 2, iPad third generation, iPhone 4s, iPod touch 5th generation and the iPad mini first generation.
iOS 13.4.1 includes bug fixes for your iPhone.
– Fixes an issue 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.
– Addresses a bug with the Settings app where choosing a Bluetooth from the quick actions menu on the Home screen would fail.
You can update your iPhone or iPod touch in the usual way, either over the air or via iTunes with your device plugged in. Over the air updating can be found in Settings > General > Software Update then follow the steps through.