Another beta for iOS 11.4.1 was released for developers on Monday, June 18, exactly one week after iOS 11.4.1 Beta 2 was sacked. Like the second beta, iOS 11.4.1 beta 3 has no new features or known fixes or bug fixes. It's likely that Apple is simply using iOS 11.4.1 to add below-surface enhancements as the iOS 12 beta release is already released.
Apple's release notes for iOS 11.4.1 Beta 3 give nothing, and the installation screen simply notes "bug fixes and improvements," just like the two previous betas. We'll continue to look for new changes that are important to the user, but at this time, it's probably just stability and security improvements.
To get the latest version of iOS 1
So far, iOS 11.4.1 is one of the least interesting iOS betas of the past few months, and that makes sense as they already exist focused on getting iOS 12 up and running in time for a public beta test release.