iOS 12 - 12.1.2 - Uncover jailbreak
Unc0ver Jailbreak Guide
Download Uncover IPA
Download Cydia Impactor from here.
Connect your device with computer and Launch Cydia impactor from the computer.
It will detect your device and then drag the Uncover IPA on to Cydia Impactor.
Enter your Apple ID & Password when prompt. It will sideload the Uncover app to your device.
After, few seconds, Uncover app appeared on your device and trust the app before running it. Go to Settings --> General --> Profiles & Device Management --> Trust the app.
Now run the Uncover Jailbreak app from your device and Tap the Jailbreak button to begin the jailbreak process.