Huawei Mate 9 is an old device equipped with kirin960. Huawei has decided to update the phone to HarmonyOS. But the base version of this update is still Android 9. And we know that Android 9 is the last version that allows bootloader unlock and root. But Huawei has EROFS technology implemented in Android 9, stopping you from modifying the system partition. But still, you can gain application-level root access and modifications can be made through props editing.

Disclaimer

• You try everything at your own risk
• This method has been tested on HarmonyOS 140 and should work for other versions
• You will lose the warranty of your phone by rooting it
• You will not be able to factory reset after root
• you will not be able to install automatic updates after root

Huawei Mate 9 Rooting Guide:

• Backup all essential data from the phone
• Unlock the bootloader of your phone (click here to buy service)
• Download the root file from THIS LINK (password=ministryofsolutions.com)
• Install latest magisk manager V23
• After that connect the phone in fastboot mode and open the extracted folder, double click MAF32.exe
• Then type ” fastboot flash recovery_ramdisk magisk_patched-23000.img ”  and press enter
• After successful flash disconnect the phone from pc
• Hold the volume up and power, and keep holding both buttons until a screen appears with the message ” your device is booting now”
• Connect to wifi and open Magisk Manager, it will ask for additional setup, and press ok then the phone will reboot automatically.
• Install root checker and verify root
• The phone must be disconnected from the cable when you start it by holding the volume up and power
• If you want to unroot flash stock recovery_ramdisk.img included in the zip file

Fix SafetyNet:

• Open magisk settings and Disable magisk check-update
• Enable magisk hide
• Tap 2 times on systemless hosts
• Go to the magic modules section
• Search and install ” magiskhide prop config “don’t reboot, go back.
• Search and install “Riru” module. Don’t reboot
• Download Safetynet Fix 2.1.3 from THIS LINK
• Tap on Install from storage and select SafetyNet fix v2.1.3 module and install it.
• Reboot Phone
• Go to magisk hide settings and tick google play service
• check SafetyNet in magisk
• Profit 
• Make sure you disable automatic updates in developer options to stop the phone from installing new updates.

Note: never install OTA after root, and do not factory reset while the phone is rooted