My iPhone 12 mini is hobbling along. A few rare apps are not usable because UI is clipped, the battery is throttling and making it sluggish, and it overheats all the time as a GPS.

Many mobile websites are unusable.

But I love the form factor and I'm going to keep it going as long as it is reasonably secure.

curious, did changing the battery make the phone faster under the latest OS?

If find that after the upgrade to the latest iOS my 13 mini has been struggling with framerate and just overall feeling laggy.

I just eBay'd a 12 mini after my camera started getting blurry. There isn't a viable flagship replacement.