Apple's iOS 12.4 introduces iPhone migration to directly transfer data from an old iPhone to a new iPhone, includes enhancements to Apple News+ and improves the security of your iPhone or iPad.
This iOS is now available on 3uTools, here are a few steps to install it on your device.
Step 1 Connect your iDevice to PC with an original USB cable and launch 3uTools.
Step 2 Go to Flash & JB → Easy Flash, select firmware iOS 12.4. If you want to update with data, please check the box "Retain User's Data". There will be a pop reminder after you click "Flash", please read it with caution.
You are recommended to back up your iDevice regularly in case of data loss.
Step 3 Keep the stabilization of network and USB connection while flashing, wait patiently for around 5 to 10 minutes. Your iDevice will be updated to iOS 12.4 after reboot.