I think you can actually install through TWRP, as long as you unroot it first.
When your phone is one and sends you the OTA and you tap Accept, it downloads it to cache.
I think then when it boots in TWRP, you can install it by choosing the update.zip in cache.
I haven't tested it yet, I'm looking for more data on this topic, but this seems to be the actual solution. (instead of the easy and time consuming solution of flashing stock recovery, updating, and flashing twrp again..)
With EMUI, it's definitely impossible to install the "native" OTA updates with TWRP. You will just get a bunch of error messages in the TWRP console when you try to install the update.zip etc.
The way (I will test it in a few seconds) would most likely be:
- Flash a stock recovery over TWRP with adb/fastboot BUT DON'T LOCK THE PHONE AGAIN AS IT WILL WIPE YOUR ENTIRE DEVICE
- Start the OTA update normally from System Settings
- When the device reboots, it should go to recovery and install the update, making you lose root, xposed and whatever you have installed
- Then, if the update was successful, reboot again into fastboot and flash back TWRP
- Then boot into TWRP, install your SuperSU again
- You should be set with it
Hint for getting the stock bootloader: Start the update to make it download all the files. They will be in Internal Storage\HwOUC. Download the update.zip to a Windows PC, extract the UPDATE.APP from it. Download Huawei Update Extractor:
https://forum.xda-developers.com/showthread.php?t=2433454 and extract the file RECOVERY.IMG from the UPDATE.APP.
With an unlocked bootloader, you can simply flash the RECOVERY.IMG onto your device just like you did with TWRP before.
As I said, I will test this in a few minutes with my Honor 8.
AND REMEMBER TO MAKE A BACKUP OF ALL YOUR APPS AND FILES BEFORE!
I will report if it went successfully!