https://wccftech.com/beta-4-of-ios-12-1-watchos-5-1-tvos-12-1-seeded-to-developers/

Apple has just released the fourth beta of iOS 12.1, watchOS 5.1 and tvOS 12.1 to registered developers. We’ll show you how you can update.

Those enrolled in Apple’s Developer Program know that the company is hard at work forging its next big software update for mobile devices including the iPhone, iPad, iPod touch, Apple Watch and Apple TV. Today, the company has released beta 4 of those updates and registered developers and go ahead and grab the update over the air right away.