[Nokia 6 Guides, News, & Discussion] hikari_calyx:
Like the alternate Nokia 8.1 Bootloader Unlock method before, here's what you need:

- TWRP accessibility with proper bootloader downgrading. You must use Chinese 7to TWRP I posted last year (In Nokia 6 Root Guide) to achieve this (either 3.1.1 or 3.2.1 are OK), so downgrading the bootloader back to Nougat is necessary.

If your phone still stay at Android 7 or 8, great, you're welcome to NB1-Collision method.

As I've introduced in Nokia 8.1 forum:

The identification to verify if the unlock key valid is located at deviceinfo partition, and here are the offsets:

SN: 0x00000010

IMEI1: 0x00002010

Still, editing the IMEI1 here will not change the actual IMEI stored at NVRAM, so you can't use this to do anything illegal.

If you know the point, you can unlock your phone without reading this guide. In case you don't, let me tell you how.

Part 0: Obtain an official unlock key for Nokia 8, and you must know it's IMEI1 and SN

Same as before, I will not provide mine, please do it yourself.

Part 1: Boot to TWRP

Skip this part if you can boot to TWRP already. Just boot to TWRP and do Part 2.

To make sure the phone will definitely boot to TWRP with proper signature, you can flash TWRP to boot partition directly:

fastboot oem dm-verity (md5)
fastboot flash aboot /path/to/D1C-0-331A-emmc_appsboot_service.mbn
fastboot reboot-bootloader
fastboot oem dm-verity (md5)
fastboot flash boot /path/to/7to-twrp.img

The extraction password of the service bootloader zip is "WLBGFIH123", in case you want to know.

Then reboot to the TWRP:

fastboot reboot

OK, now you've entered the TWRP.

Part 2: Dump the deviceinfo partition and hack it

If you're familiar with adb commands, here's how:

adb shell dd if=/dev/block/bootdevice/by-name/deviceinfo of=/tmp/deviceinfo.img
adb pull /tmp/deviceinfo.img

The rest of the procedure are straight forward. Use a Hex Editor to edit the deviceinfo partition:

Offset(h) 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

00000000 46 49 48 45 32 50 5F 42 00 00 00 00 01 00 00 00 FIHE2P_B........
00000010 4E 42 31 47 41 44 32 37 38 30 30 31 32 33 34 35 NB1GAD2780012345
00000020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................

Offset(h) 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

00002000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00002010 31 32 33 34 35 36 37 38 39 30 31 32 33 34 37 00 123456789012347.
00002020 xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx 00 xxxxxxxxxxxxxxx.

And save it as deviceinfo_mod.img.

Push it back to your phone, along with new version of emmc_appsboot, either service or retail are OK - you can extract it from recent OTA packages.

adb push /path/to/deviceinfo_mod.img /tmp/d1
adb push /path/to/D1C-0-562H-emmc_appsboot.mbn /tmp/d2
adb shell dd if=/tmp/d1 of=/dev/block/bootdevice/by-name/deviceinfo
adb shell dd if=/tmp/d2 of=/dev/block/bootdevice/by-name/aboot
adb reboot bootloader

Part 3: Unlock the bootloader

fastboot flash unlock /path/to/unlock.key
fastboot flashing unlock_critical

Your phone will reboot immediately. Don't stop right here, execute following command straight forward:

fastboot oem alive

When fastboot responsed OKAY, please proceed:

fastboot flash unlock /path/to/unlock.key
fastboot oem unlock-go

All done. Your phone has unlocked bootloader.

Part 4: Restore original deviceinfo and reinstall stock firmware with OST LA

fastboot flash deviceinfo /path/to/deviceinfo.img

I needn't to mention how to flash stock firmware with OST LA or NOST.

FYC, firmware can be downloaded from https://fih-firmware.hikaricalyx.com/hmd_en.html#d1c .

Good luck then!

Specially thanks to HMD Global for releasing official Nokia 8 bootloader unlock, otherwise it would be impossible.