I have an iPhone SE (2017), the battery is at 88 % and I had about a day of battery life with iOS 13. Yesterday, with iOS 14, I watched my battery dropping 1 Percent about every 4 seconds. After a couple of minutes it went from 62 % to 10%. I made a screen recording from 39% to 20% - it's hilarious in a way but primarily it's very concerning. My Android-user-friends are now laughing at my iPhone connected to the powerbank all the time 🤣🤣🤣

Update on iOS14: This morning I unplugged my iPhone SE (2017) at 100%. A few seconds later it restarted itself and greeted me with the power-saving-mode at 10%. This phone is absolutely useless now!