Late last week, Apple released a much needed update to iOS 15 with iOS 15.4.1 and iPadOS 15.4.1, both of which are relatively minor but one feature sticks out over the rest. With this release, Apple fixes an issue which could have caused devices running iOS 15.4 or later to have battery drain issues.
Since iOS 15.4, there may have been an issue with some users seeing issues with the battery draining faster than usual, hopefully this releases fixes the problem for many people. There are also some fixes to some MFI hearing aid devices, some of which could drop connection to the iPhone.
The update was released last week and can be downloaded by going to Settings > General > Software Update.