I had the same problem with a new iphone 7. (1 month old !!! ) I send it back to repair and all repair did was to revert to ios 14.1 my conclusion is that there IS a problem with battery drain on ios 14.2 and apple KNOWS it's a problem as usual they do not communicate about it and that is creating a lot of distrust against their products. I would be nice if they'd withdrawn the 14.2 update because if my phone is set to auto-update I will have the same problem again and again...