[Honor 8 Guides, News, & Discussion] sic0048:
I just bought the Honor 8 and immediately unlocked and rooted it via Magik. Of course not long after that, I get a notification that there is an update available. You obviously cannot update the phone by simply pressing the "update" button since we have a non-stock recovery. I did a fair amount of research to find out how I could get the update and I wanted to share what I found. All of this information is out there already, but generally speaking it is spread out in many different threads. Hopefully these directions can help someone else.....

First, the usual disclosures.....

I am not responsible for bricked devices, dead SD cards,
thermonuclear war, or you getting fired because the alarm app failed. Please
do some research if you have any concerns about features included in this GUIDE
before flashing it! YOU are choosing to make these modifications, and if
you point the finger at me for messing up your device, I will laugh at you.

1) Make a NANDroid backup using TWRP: if the new update locks the phone, you will need this backup to restore data after unlocking it

2) Unroot your phone: honestly I did not do this step myself because I simply didn't think about it. The update process worked for me without unrooting but I am also using Magik which doesn't alter the system files. To ensure success I would definitely recommend you unroot. You will have to reroot the phone after the update regardless if you unrooted or not, so you aren't saving any steps by keeping root at this point. If you have used a different root method besides Magik, you must unroot prior to attempting an upgrade.

3) Obtain stock recovery.img file: the update won't work with TWRP as your recovery, so we need to flash the original Huawei recovery to replace TWRP. If you already have a copy of the stock recovery skip to step 4. If you are like me you don't have a copy of the stock recovery image on hand and we will need to extract it from the stock ROM image. Using a computer (not your phone) download the stock ROM image for your device. This website seems to have a list of recent versions and it is where I downloaded the L14 B389 version that I used.

Download the Huawei Update Extractor software and unzip the folder on the computer. Open the HuaweiUpdateExtractor app and use the software to extract the "Recovery.img" file. Here is a Youtube video showing how to do this. Please note, although the video shows several files being extracted you only need to extract the "Recovery.img" file for our use. Move the stock recovery image to your ADB folder so you can flash it in step 4.

4) Flash the stock recovery image: use the stock recovery file and flash it to recovery using the same instructions as you used to flash TWRP in the first place. If you need a refresher, look at section 2 (parts 1-5) of the first post in this thread. Just make sure you substite the name of the stock recovery image instead of the TWRP.img

5) Reboot into system

6) Install Update: go to the Settings - System Update menu on your phone. In the upper right corner, click on the three dots and it will bring up a menu where you can choose "Download latest full update". Click on this. This will start the update process by downloading the full ROM and not just the smaller update package. For me the package size was approaching 2gb, so make sure you are ready to handle that size transfer. After the download is complete, start the update process. I was nervous at first, but everything went fine. If for some reason the update fails, I would reboot and try again. I did have one failure, but I cannot explain if it was a bad download, or something I did wrong (like not unrooting the phone prior to attempting the update). It worked fine the second attempt.

7) Reboot: the phone will reboot and you should check the status to make sure you are on the latest version.

8) Flash TWRP recovery: I read where people said full updates would lock your phone and you would have to start from scratch unlocking it (and therefore wiping all data). This was not the case for me and this update using this method. I was simply able to flash TWRP again. You should be a rock star at flashing recoveries by now so get to it and flash TWRP again. If your phone is locked, then read the note at the bottom of this post.

9) Reboot into system

10) Flash Magik zip: reboot into recovery and flash Magik zip to get SuperSU.

11) Install Magik modules: reboot into system. Reinstall any Magik modules you use as they don't get carried over from the previous installation.

12) Enjoy your updated phone

If for some reason the full update did lock the phone, then you will need to unlock it again before you can flash TWRP. You have already done this before, so use whatever method was successful for you. Obviously this will fully wipe your phone. After flashing TWRP and Magik, I would make a backup of that raw "stock" image just in case this next step doesn't work. After making the backup, you can try to restore just the data partition of the NANDroid backup you made in step 1 (click restore in TWRP, select the backup made in step 1 but deselect everything except the "data" partition before starting the restore process.) I have never done this, but I have read it will recover all your data (apps, etc) without affecting the system partition and therefore it won't mess up the upgrade. I would not recommend doing this if going from Marshmallow to Nugget or Nugget to Oreo however. In those cases, it is better to simple start fresh and redownload all of your apps.