Apple has released iOS 12.1.1 beta to developers for testing. The build number is 16C5036c.
The beta contains bug fixes and improvements to iOS 12.1 which was just released yesterday. Additionally, iOS 12.1.1 requires that publicly-trusted Transport Layer Security (TLS) server authentication certificates issued after October 15, 2018 meet the Certificate Transparency policy to be evaluated as trusted on Apple platforms.
Known issues: After upgrading to iOS 12.1.1 beta, you might be unable to select the voice used for VoiceOver and other Speech products.
Developers can download the iOS 12.1.1 beta from the link below...