Apple has released iOS 12.5.1 for older iPhone models. The update is rather small and includes a bug fix for the Exposure Notification system for COVID-19.
iOS 12.5.1 is only available for older devices that are not able to run iOS 14.3.
Users who have an eligible iPhone can check for the available iOS 12.5.1 software update via Settings > General > Software Update.
Always backup your device before installing any system software update.
Remember, Exposure Notifications are not available in all regions, as it requires a separate app provided by a local government, state, or health authority. You can check your state or national health authorities for information on Exposure Notification support, but most states in the USA do not have apps to support the feature. Even those states with an app to support the feature do not necessarily have widespread adoption by their populations either, so it remains uncertain how broadly used the Exposure Notification system is.
The Exposure Notification system works in conjunction with an aforementioned health app by sharing secure Bluetooth data with other nearby devices, and determining if an anonymized match has tested positive for COVID-19, in which case your iPhone would get a notification to let you know you’ve been near someone with COVID-19.
You can learn more about enabling COVID exposure notifications here if you are interested in doing so, but remember most US states and many countries do not have apps that support the feature, and the feature is opt-in only.