Public testers, Apple just released the first public beta for iOS 12.1.2 on Tuesday, Dec. 11. The company had already released the developer beta on Monday, Dec. 10, and just like clockwork, the public beta version was right on its heels.
Unfortunately, with the new iOS 12.1.2 public beta for iPhones, you won't see any new features. We didn't expect it to ship with any bells or whistles either since the developer version didn't have any itself. There seems to be only the standard "not talked about" bug fixes and security patches, as well as one issue resolved with core audio on some iPad models. As for issues that persist, Apple only lists one that needs to be addressed, though there are likely more than that.
Accessibility Known Issues
Some user interface elements are inaccessible to VoiceOver in the "Electrocardiogram (ECG)" and "Irregular Heart Rhythm Notification" sections in Health > Health Data > Heart. (46505168)
Core Audio Resolved Issues
Audio performance when using some third-party apps is improved on iPad Pro 12.9-inch (3rd generation) and iPad Pro 11-inch models. (46037111)
Fixing small bugs and security vulnerabilities is not bad, by any means, as updating should result in a more stable build of iOS, but as this is the first version of this particular beta, there could be new bugs not found on 12.1.1, so be aware of that.
To update your iPhone to iOS 12.1.2 public beta 1, you first need to sign up for the beta program and have a valid configuration profile. If you have iOS 12's "Automatic Updates" enabled, you can let the software update overnight. To download the beta right now, launch the Settings app, select "General," then "Software Update." Tap "Download and Install," then follow the on-screen prompts.