iOS 10.3 beta 3 with Find My AirPods and other enhancements and macOS Sierra 10.12.4 beta 3 with Night Shift Mode and other perks are both now available for public beta-testing, assuming you've enrolled in Apple's Beta Software Program. After signing up on the web at beta.apple.com, deploy a special configuration profile on your iPhone, iPad, iPod touch or Mac and you'll be able to install the latest beta over-the-air via Apple's standard Software Update mechanism.
iOS 10.3 beta 3
Apple today seeded a third beta of iOS 10.3 to members of the Apple Developer Program. It's nothing to write home about in terms of new stuff, with the notable exception of a curious new section suggesting that iOS 11 is likely going to be 64-bit only. The first beta of iOS 10.3 introduced a reworded prompt when launching 32-bit apps.
In iOS 10.3 beta 3, there's now a dedicated section within the Settings app where any outdated apps installed on the user's device are named and shamed.
Apple this morning seeded to members of the Apple Developer Program a third beta of what would become the iOS 10.3 software update with Find My AirPods and a bunch of other new features. iOS 10.3 beta 3 (build 14E5249d) is available over the air via Software Update on devices with an appropriate configuration profile installed. We'll update the article with possible new changes discovered in beta 3 if we encounter them. New betas of macOS Sierra, watchOS 3.2 and tvOS 10.2 are available for developer testing, too.