I'm using a first generation IPhone SE (the old one, not the new one) and hase just updated to IOS 15.1 on 5 December.
Since then the battery has discharged really quickly over and over again. I've done some testing and spotted some apps that had reverted to settings I didn't want, so this may help, but I've noticed that using Voice Over and Siri seems to be eating away at the battery more than usual.
Has anyone else spotted this? Is it just the universe telling me that I need to buy an new IPhone?