SOLVED (at least for me)! Over several weeks after upgrading from 13.7 to 14.4.x I tried turning off MANY Settings and offloading all 3rd-party apps -- to no avail. Still sluggish, overheating, and fast battery drain anytime screen was on. An apple-support tech mgr suggested doing a full Settings&Content Reset to confirm if a hardware problem. And phone worked fine as as empty new phone... so was definately confused software. So I re-did a full reset and restored from iCloud backup and it SOLVED this problem on my iPhoneSE(1st gen). So do THIS: do a full icloud-backup (pay 99 cents for 1 month increased storage) (Settings/General/RESET ALL CONTENT AND SETTINGS (As it reboots it will reset/reinstall to 14.4.2) Follow phone setup steps and login into your apple ID and restore from the iCloud backup. After doing those my SE was back to normal!! :)