Now again type adb devices and hit Enter.
This time you can see that the device is authorized and we’re ready to boot our phone in fastboot mode.
To boot the phone in fastboot mode, type adb reboot bootloader and press Enter.
Look at your phone screen, it must be in the fastboot mode now.
Finally, type fastboot oem unlock and hit Enter to complete the bootloader unlocking process for your K20 Plus.
Now the bootloader is unlocked. We can verify the unlock status with command, fastboot getvar unlocked
You can see the result is “unlocked: yes” it confirms that we’ve successfully completed the unlocking process.
Now to get out of fastboot mode either you can remove and reinsert the battery to boot the phone or restart it with the command, fastboot reboot as shown above.
As long as the bootloader remains unlocked, everytime you boot the phone you’ll be greeted with this warning message ” Your device software cannot be checked for corruption. Lock the bootloader.” This is normal you just have to press the power button once to boot the phone normally.
For any queries, feel free to leave a comment below.