https://www.theregister.co.uk/2018/08/14/apple_pulls_ios_beta/

Apple has pulled the latest beta of its iOS platform software after less than 24 hours in the wild, and without explanation.

This year’s release, iOS 12, is intended to be a performance update with Apple stating that it sought to improve performance on older, lower RAM devices like the iPhone 6. The platform release is available for iPhones and iPads going back to 2013: the iPhone 5S and the original iPad Air.