fastboot oem device-info Output should show: (bootloader) Device unlocked: true
Use volume keys to highlight “UNLOCK THE BOOTLOADER” and press power button to confirm. Unlock Bootloader Nokia 3.4
But one day, a critical security patch arrives. You can’t install it normally. You have to re-lock the bootloader — which requires flashing stock firmware first. That’s another story. Unlock Bootloader Nokia 3.4
adb reboot bootloader The phone screen goes black, then shows the screen — a tiny white text on a black background. Unlock Bootloader Nokia 3.4
To verify: Reboot to bootloader again and type: