With the incoming iOS 15.4.1, this has been successfully fixed which is a good thing.
What the update has additionally offered is a security update.
If yes, download and install it.
source: www.techworm.net
Apple releases iOS 15.4.1 which fixes battery drain issue
Apple has finally released iOS 15.4.1 which patches the battery draining issues triggered by iOS 15.4. It doubles as a security update too.
