iPhone 5 is not supported right now in iOS 11. Meanwhile iPhone 5s is the next iPhone to be dropped in iOS 12 because of Five reasons:
1. A7 This aging chip overheats a lot similarly founded on A5X. Especially in iOS 11
2. Cannot scan cards, does not have 240fps in slow mo.
3. Lacks NFC, lacks barometer.
4. The iPhone 5s is only clocked at 1.3 Gigahertz just like the iPhone 5
5. Excessive battery drain. iPhones/iPads on their Latest final iOS update one of the symptoms that they will be dropped soon is a extreme battery drain. Unlike iPhone 6/6S/SE and newer they have much better battery life like 2 hours longer in iOS 11 than on 5S no matter if you have exchanged the battery as new.