[LineageOS Questions & Answers] fepoulpa:
Y9 2018 running Android 9 Custom ROM

(Havoc OS+MicroG)

Hi, so I landed on this forum a year ago, thinking that it would be impossible for me to one day unlock and tweak my Huawei Y9 2018.

Today everything works fine for me as I managed to install a custom ROM after unlocking the bootloader. I'll detail you step by step what I did, I'm new here so this is obviously not the only way, I'm just telling you what I did to make it work, and of course I am not responsible if anything wrong happens to your device, many times during the process I did things wrong and I bricked the phone, but you should always be able to come back to step 1 and restart fresh.

STEP ONE: INSTALL STOCK ANDROID 8 FIRMWARE (before June 2018 security patch)

For this step all you need is an SD card (and a computer if the phone is bricked).

Go to here and type in your phone model, I have the FLA-LX3 so I took this file which is at the bottom of the result list.

Afterthat extract the zip and copy the filed called update.APP to a folder called dload in your SD card.

Turn off your phone with the SD card placed inside and boot it from the SD card. To do that, you have to press volume up and power button at the same time for 5 seconds.

The installation should start and you will soon boot back in Android 8.0.0. Quickly reach the settings to check if you have successfully downgraded before June 2018. Otherwise the rest won't work. Finally, rename dload folder in your SD card to something else so that next time your phone won't try to install a system from the SD card.

STEP TWO: FIND YOUR BOOTLOADER CODE

If you already know your bootloader code, directly go to step 3.

This is a tricky part, as you already know there is no official way to get your bootloader code. There are different approaches to get the code. Both need a computer.

A free one can be found here but I didn't use it personally. It's a simple brute force attack to find the code, it can be extremely long so most probably not the best one.

A second option, which is most used is the DC-unlocker tool for Windows that will find the bootloader code in couple of seconds. You have to use 4 credits (4$) to perform the action "Huawei Qualcomm Read Bootloader Code (up to Android 8)". The tutorial can be found here

Once you know your code, save it everywhere !!!

STEP THREE: UNLOCK BOOTLOADER

For this step you will need a computer with ADB and Fastboot commands. (download the command line tool for Windows/Mac/linux from here)

Go to phone settings, activate OEM unlock and USB debugging (you might need a WiFi connection to enable OEM unlock). If you type adb devices in your shell you should see you device in the list.

Type adb reboot bootloader to enter fastboot mode.

If you type in fastboot devices you should see again your device in the list.

Type in fastboot oem unlock *paste your code here*

On our device confirm unlock and the device will reboot after a factory reset.

STEP FOUR: FIND THE RIGHT GENERIC SYSTEM IMAGE

There is no official custom ROM for Huawei Y9 2018 but the phone is compatible with Generic system images, which are universal ROMs (all listed here). To be sure quickly reach the browser to download Treble Check app from here. This app will tell you wether or not you can install GSI images on your phone. If Projet Treble is ticked then you are good to go. If Seamless updates is ticked then you have an A/B system, if not then you have an AONLY system. Finally the CPU Architecture tab should tell you if you are on ARM64 or something else.

The GSI rom I chose is Havoc OS, it is the most compatible for Huawei phones. It is an Android 9 rom built on top of Lineage OS and adds up some functionalities, fixes for Huawei phones, and signature spoofing for MicroG to work. Go to this link and choose the right Havoc version based on the Treble Check app.

STEP FIVE: INSTALL HAVOC OS

Once you downloaded the connect img file connect your phone again and enable USB debugging, type in adb reboot bootloader to enter fastboot, and enter fastboot flash system *GSI rom path*

Once done, unplug device from computer and reboot to eRecovery by holding power and volume up for 5 seconds (just like in step 1 so make sure no SD card with dload folder is placed inside the phone). Once in eRecovery perform a factory reset and after that hit reboot system. Your device should now boot with Havoc OS !

STEP SIX: install F-Droid MicroG and Aurora Store (Alternatives to Google ecosystem)

Go to the browser and install F-droid from their official site. Next add the MicroG repo to F-droid to install and activate all the replacements to Google services. You can finally install Aurora Store from F-droid which replaces the official Play Store.

That's it folks!