If you try to use the bootloader unlocker apk from Nokia and your Nokia 8 has an android version that's past a certain version, the apk will flat out fail with a "Device not support." error message. And chances are, your Nokia 8 will be at an incompatible android version. So to unlock the bootloader, you will need to downgrade your phone to a legitimate version of android 8.1.0 so the apk will not error out and get you a verification code. This guide will show you how. NOTE THAT THIS METHOD WILL ERASE ALL INTERNAL DATA ON YOUR PHONE.
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This update zip is what you need for the TA-1004: https://android.googleapis.com/pack.../f9cb380bd9c2bf1b6ddebcab9dcf389843eb2d39.zip
It may be different for the TA-1012, but according to that earlier post, it does not seem to be the case. Nevertheless, just to be safe, here's the zip for the TA-1012: https://android.googleapis.com/pack.../139c94fd08f52fbd3b852ab4ef5c6515fffb784e.zip (I don't have a TA-1012 so I wasn't able to test this particular zip.)
So basically, to make sure there's no problems, make sure in the Developer's options on the phone that OEM unlocking is enabled, then put your SD card into the phone. Plug the phone into your computer. Copy the update zip that you need somewhere onto the SD card. Disconnect the USB cable. Shut down the phone. Then, while holding down the Volume Up button, reconnect the USB cable. You should see a sad android with "No command" displayed. Now release the Volume Up button. Then hold down the power button and then JUST PRESS once on the Volume Up button. You should be at a recovery menu. Using the volume keys, scroll down to the 'Apply update on SD card' option and select it. Select the zip that you copied over to the SD card earlier and then let it install for a while. It will probably pop up with a 'timestamp too old' error, but just ignore this. The update will install anyway. Then once it's done, do a factory reset on the phone and then shut down. MAKE SURE THERE'S NO SIM CARD IN THE PHONE.
Now that's out of the way, boot the phone up again and just click through the first-time setup screens but DO NOT ENABLE WI-FI or any kind of internet connection. We don't want the phone to update itself back to Android 9. Now plug the phone in again. Copy the bootloaderunlocker apk from Nokia's website onto the phone. Install it. Put in the email address you want the unlock key emailed to. Then voila! You'll get the verification code. Put it into the form on Nokia's website and you'll be emailed an unlock.key file. From there, the site will tell you how to proceed.
A HUGE thanks to: THMSP and frankoid
They did all the work. <3
My nokia 8 TA_1012 September update this method possible to downgrade