If you want to jailbreak, you can downgrade to iOS 12.4 as soon as possible if you have upgraded to iOS 12.4.1 or IOS 13 beta.
This method is more risky, but it allows you to roll back to iOS 12.4 without completely resetting the device. In addition, this method is much faster than the second.
How To Downgrade iOS 12.4.1 to iOS 12.4:
- Turn off Find my iPhone in Settings > iCloud > Find my iPhone.
- Download the iOS 12.4 file for your device from the link below: iOS 12.4 for iPhone and iPad.
If you download the firmware file via Safari, make sure that you have automatic unzipping disabled. It is better to use Chrome or Firefox. It will also help if you rename the file .zip to .ipsw.
- Connect your iOS 12.4.1 device to your computer.
- Launch iTunes on your computer and select your device in the upper left corner. From the left menu, select the Overview tab.
- Hold down the Alt/Option key on your Mac keyboard or the Shift key on your Windows PC keyboard, and then click check for updates instead of restoring.
- Select the downloaded iOS 12.4 ipsw file.
- iTunes will notify you that your device will be updated to iOS 12.4.
- Click Update.
- Wait for the process to complete.
Now you can make Jailbreak iOS 12.4.