I'm not convinced that the 80% limit is anywhere close to all that it is cracked up to be. Yes, there are articles about the "advantages" of doing this and I have tried it for about 6 months and all that I have really concluded is that you have to charge the battery more often using this method.
The battery still charges to 100% "on occasion", but I'm not sure what that really means. "On occasion" seemed to be a few times each month for me, but I imagine that other users are seeing quite different "occasions".
I am going to continue to use the method that I've used for years with other phones....simply enabling Optimized Battery Charging, ignoring the 80% limit setting....if it is present....and connecting the phone to the power adapter at night and leaving it connected all night.....every night.
The battery starts at 100% each day, so I get more time from a single charge and rarely have to charge the phone again during the day.
Over the long haul, the 80% method might result in a month or two more battery life, but as long as I'm getting 4-5 years from the battery, I could care less that someone might get another month or two from their battery.
Watch for more gimmicks on newer iOS versions regarding battery life. After all, if 80% is better than 100%, then 70% must be better than 80%.
My opinion......worth about as much as you had to pay to view this page......users in general are spending way too much time checking and worrying about the battery. It's a battery folks, you will have to replace it at some point unless you trade up to a new phone every 2-3 years. I have better ways to spend my time.