If one lesson can be learnt by all this it is to stop blindly leaping to every new iOS release.
Gordon Kelly is a frequent critic of Apple so I have always taken his iOS update reports with a grain or three of salt. But with the recent 13.x releases, I now wish I’d listened to him and held fast to iOS 12.
My SE, which usually held a good battery charge all day, drains down to 5% within an hour simply sitting on my desk.
My SE is 2+ years old so, on the off-chance, I’m having a new battery installed this week. If I still see a drain, I’ll know it’s iOS.
I have turned off automatic updates and am holding fast, for better and worse, at 13.2.1.
Update, 2019-11-13: Took my iPhone to an Apple certified service shop. The repair guy hooked my phone up to his diagnostic computer and it said the battery had gone through 600 recharge cycles; Apple says the battery has a lifetime of 500 cycles. So yeah, the battery was shot. The Battery Health setting is an OK criteria (mine was at 88%) but not the decisive one; it’s the number of cycles that is decisive. But the user cannot see the number of recharge cycles a battery has gone through, only a technician. Charging the phone up now; hoping for good times ahead.