Based on LineageOS 15.0 – Android 8.0.0
First Android ROM released for Huawei Y6 (2018).
Unlock your Bootloader!
Download the ROM
Enter fastboot mode on your device
Flash the ROM with: fastboot flash system [LOCATION AND FILE HERE]
Your device will reboot to erecovery and will do a factory reset so make a backup of important things!
Reboot your phone after the factory reset