Root and TWRP is now available for Huawei Mate 9 smartphone. It got a functional TWRP with some limitation but you can get root access after flashing phh's supersuser (super user alternative because superuser is not tested yet) via TWRP recovery.
This TWRP can be flashed on all version of Huawei Mate 9. It was tested on Huawei Mate 9 Europian version MHA-L29.

Contributor Tkkg1994 was able to port TWRP 3.0.2-1.


WARNINGS• Flashing TWRP will need a unlocked bootloader and bootloader unlocking process will wipe/format/delete all your data/internal storage . So Before proceeding to flashing guide make sure to backup your data.
According to the TWRP Maker he has not yet fully tested the problems of dm-verity v2.0 introduced in Nougat. So as long as you don't need to modify /system, keep it read only. If you want to edit something inside system, make a backup until He can tell you more about it.


SUPPORTED DEVICES
• MHA-L29XXX devices
• MHA-L09XXX devices
• MHA-AL00XXX devices
• MHA-TL01XXX


How To Unlock Bootloader

1.Call Huawei in the HiCare app, request the bootloader unlock code there you have to give your email, IMEI, serial number etc.
Or You can login and Request your bootloader unlock code from Huawei Unlock Tool

2.. Install minimal adb and fastboot drivers from here: ADB and Fastboot drivers

3. Plug in your phone and make sure all huawei drivers got installed.

4.. Enable developer options in settings by going to setting > about > Tap Build no. 10 times.

5. Enable OEM unlock, enable USB debugging (both are in developer options)

6. Open the adb tool you installed recently.

7. Type fastboot devices
(now a device number should show up)

8. Type fastboot reboot-bootloader
(your phone will now boot into bootloader, if not, you haven't set up drivers or adb/fastboot correctly)

9. This step will wipe all your data!
Type: fastboot oem unlock xxxxxxxxxxxxxxxx (xxxxxxxxxx is your unlock code)

10. Ones it's done type: fastboot reboot.
Your phone will reboot and you have an unlocked bootloader!

11. You can now go on installing TWRP on your device in next Steps.


How To Flash TWRP

1. Make sure you again enabled OEM unlock and USB debugging in settings, because your phone just have just reset by bootloader unlock you have to enable it again.

2. Download the TWRP recovery from below.

TWRP V3.0.2-1

3. Open the adb/fastboot application on your pc and go to the directory where you downloaded TWRP img file. Rename your TWRP to recovery.img

4.Boot your phone into download mode
First method• type: fastboot reboot-bootloader while connected to pc.
Second method• power off your phone, hit power on and volume down until it boots to download mode

5. Check again if there is written on screen: unlocked phone

6. If yes then type in adb/fastboot terminal:
fastboot flash recovery recovery.img

7.Now Type: fastboot reboot

8. Now boot into recovery by pressing: power+volume up+volume down button at the same time . (After switching off your phone)

9. Enjoy your new twrp.


How To Root

1. supersu is not tested yet so We will use this root method: Phh's superuser

2. Download latest official phh superuser zip r275 version.

3. Put the zip on your external sd card of your phone (since we can't access /data in twrp)

4. Boot into twrp and flash the downloaded file zip from external Sd card.

5. Now reboot to system.

6. Install latest Material phh apk: From Here

7. Now you are rooted, congrats!


Known Issues

• Encryption is not supported yet!
• MTP/OTG doesn't work yet


Credits

• @jcadduono
• Tkkg1994


Source

Xda thread