As well as the iOS 14.3 software update, Apple also released another software update for older devices, iOS 12.5.
The iOS 12.4 update has been released for the iPhone 5s, iPhone 6, iPhone 6 Plus, iPad Air, iPad mini 2, iPad mini 3, and iPod touch six generation.
The software brings the ability to use the COVID-19 exposure notifications to these devices, it also comes with a range of bug fixes and performance improvements.
iOS 12.5 lets you opt-in to the COVID-19 Exposure Notifications system for your iPhone. System availability depends on support from your local public health authority. For more information see covid19.apple.com/contacttracing
If you own an iPhone 5s, iPhone 6, iPhone 6 Plus, iPad Air, iPad mini 2, iPad mini 3, and iPod touch six generation, you can install the update by going to settings > General > Software Update.
Source 9 to 5 Mac