Because there is no official tool, you must use unofficial methods that typically involve specialized service tools or community-driven exploits: Hikari Calyx Method
Open your command prompt or terminal window inside the folder where you extracted the ADB Platform Tools. Type adb devices and press enter.
Go to Settings > About Phone and tap "Build Number" 7 times.
Now you can flash custom images:
If you want the absolute "coolest" but also riskiest method, there is the method.
The most documented, free method for unlocking the Nokia 3.4 bootloader was developed and shared by a well-known XDA Developer, hikari_calyx . It involves flashing a prototype engineering ABL (Android Bootloader) partition from a Nokia 3.4 pre-production model. This modified bootloader bypasses the security checks that block the unlock command.
On PC:
Unlocking the bootloader does not automatically root your phone. Instead, it opens the door so you can install custom recovery environments, flash new software, and gain administrative access later. Why Is Unlocking the Bootloader Better on Nokia 34?
Factory software updates often include heavy background services. These services overload older processors and limited RAM. A custom operating system removes this bloatware, which immediately speeds up system animations and improves app loading times. Extend the lifecycle of your phone
You can root your device to remove "bloatware" or use kernels that optimize the aging Snapdragon 460 for better battery life or smoother UI transitions. Extended Longevity: nokia 34 unlock bootloader better
Open Device Manager on Windows. If you see a yellow triangle next to your device, manually update the driver to "Android Bootloader Interface."
It is essential to be cautious.