I've got the s21 FE with one UI 4 and android 12 and yes..my battery was draining like mad..ive had to put it from 120hz to 60hz and screen from bright to neutral colours just to get the most out of it..Im hoping they fix it 😊
It may settle back to normal after a few days, the same happened with my Nokia to start with after the Android 12 Update. Now it's back to sipping through 20% a day