iOS 13.1 may be the latest major update that Apple has released, but today it rolled out an iOS 12 update for older iPhone and iPad models.
iOS 12.4.2 is now rolling out to older Apple devices that aren't compatible with iOS 13. That includes the iPhone 5, iPhone 6, and iPhone 6 Plus as well as the original iPad Air, iPad mini 2, iPad mini 3, and the iPod touch (6th Gen).
There's no word yet on what's included with the update to iOS 12.4.2, but it seems likely that it's bringing some security fixes to the older devices that aren't able to update to iOS 13. This way, they're not stuck with vulnerabilities just because they're too old for the complete iOS 13 update.
If you've got a compatible device, you can update to iOS 12.4.2 by going into Settings > General > Software Update.
Also rolling out today is an update to watchOS 5.3.2 for the Apple Watch Series 1 and Series 2 models. Apple says that the update includes security patches. You can grab the watchOS 5.3.2 update by launching the Watch app on your phone and selecting General > Software Update.