[Honor 8 Guides, News, & Discussion] hackslash:
With the Oreo update out, several Honor 8 users have become impatient :p and want to install the update in advance of their regional releases. This guide will help you accomplish this. I won't be held responsible for any damage to your device including but not limited to bricks, explosions, etc.

Before you upgrade, ensure that

Your bootloader is unlocked. Rebranding involves flashing modified recovery images which isn't possible with a locked bootloader.

You're on a dual SIM device. Chinese FW don't support single SIM devices and you'll lose your IMEI, hence no cellular connection. It is possible however to upgrade to Oreo with SIM working but there are some trade-off(s), read the last section.

Oreo FW doesn't include GApps. However, they can be downloaded from the Huawei AppMarket (comes pre-installed).

The FW is still in beta. Bugs are to be expected. Just know this isn't the place for that.

Step I - Rebrand to Chinese FW

Let us get started. Our first job is to rebrand to Chinese FW. Piece of cake. Just follow the steps below, precisely:

Backup any important data, especially those precious cat photos.

Download this file: https://drive.google.com/open?id=1eQHOfsCidKhE6AxXZKHkwwjfqYEEjCR6. Extract the archive and place the .img inside in your SD card or Internal Phone storage.

Download the two No-Check recoveries and place them in the root of your Internal Phone storage:

Recovery 1: https://drive.google.com/open?id=0B4SPRmBNsTefSWZLSWxpWGd6QkE
Recovery 2: https://drive.google.com/open?id=0B4SPRmBNsTefSVhxMWFoa01wams

Download Chinese B396 Nougat FW and copy them to /data/update/HWOTA/ folder (create folders if they don't exist):

Main Update File: http://update.hicloud.com:8180/TDS/data/files/p3/s15/G3109/g1699/v143478/f1/full/update.zip
Customization File: http://update.hicloud.com:8180/TDS/data/files/p3/s15/G3109/g1699/v143481/f1/full/FRD-DL00_dualcu_cn/update_full_FRD-DL00_dualcu_cn.zip

Reboot your device to TWRP. Navigate to Install > Install Image > Select the .img file > Check OEMINFO as the partition to flash the .img to. Start the install process and wait for it to finish. Don't reboot the device after installation.

We'll now install the modified recoveries. Using either TWRP's terminal or ADB Shell (as root 'su'), execute the following:

dd if=/sdcard/FRD_RECOVERY_NoCheck.img of=/dev/block/bootdevice/by-name/recovery_a
dd if=/sdcard/FRD_RECOVERY2_NoCheck.img of=/dev/block/bootdevice/by-name/recovery2_a

Let's prepare the installation of the FW. In the same TWRP terminal or ADB Shell, execute the following:

echo "--update_package=/data/update/HWOTA/update.zip" > /cache/recovery/command
echo "--update_package=/data/update/HWOTA/update_full_FRD-DL00_dualcu_cn.zip" >> /cache/recovery/command

Reboot your device to recovery from TWRP. This time, the device will reboot to NoCheck recovery and start the installation process.

Step II - Flash the Oreo update

The steps to flash to Oreo are same as rebranding. You'll follow the exact same steps as above, keeping the following things in mind:

Your bootloader might relock after the update. Unlock it and flash TWRP again.

There is no need to reflash the OEMINFO file as we've already done that, so skip it.

Instead of installing B396 FW, we'll flash the Oreo firmware. At the time of writing of this guide the latest available firmware was B511:

Main Update File: http://update.hicloud.com:8180/TDS/data/files/p3/s15/G3109/g1699/v142251/f1/full/update.zip
Customization File (Public): http://update.hicloud.com:8180/TDS/data/files/p3/s15/G3109/g1699/v142251/f1/full/public/update_data_full_public.zip
Customization File (OEM): http://update.hicloud.com:8180/TDS/data/files/p3/s15/G3109/g1699/v142251/f1/full/FRD-DL00_dualcu_cn/update_full_FRD-DL00_dualcu_cn.zip

You'll copy the above files to /data/update/HWOTA. Also, modify the commands executed in Step 7 to:

echo "--update_package=/data/update/HWOTA/update.zip" > /cache/recovery/command
echo "--update_package=/data/update/HWOTA/update_data_full_public.zip" >> /cache/recovery/command
echo "--update_package=/data/update/HWOTA/update_full_FRD-DL00_dualcu_cn.zip" >> /cache/recovery/command

Reboot your device and tada, you're on Oreo, yum, yum!

The alternate way for Single SIM users

It is the same as the above mentioned steps. Follow only Step 2, don't flash the OEMINFO file. However there are some trade-offs like:

The customization file won't flash due to region mismatch so you'll be left with a borked installation i.e. only some system apps, no keyboard, no app store, broken build number, non-working themes, etc. etc.

Remember, we did it all for that pesky SIM so don't complain.

If you face any errors, don't hesitate to slap me in the comments below. I'm waiting...