Only a few days after Apple released a fifth beta of iOS 11.3, today the company has pushed out beta 6 to registered developers, featuring a build number of 15E5216a.
This sixth beta release is not yet accompanied by a corresponding tvOS 11.3 beta.
The release notes for the latest beta contain no significant changes, suggesting that Apple is primarily polishing iOS 11.3 for a final release, which is expected to be available by the end of this month.
