If you have already secured an unlocked bootloader, the general process follows these steps: Understanding Android Custom ROM installation process

Known for high customization, though often based on older Android versions for this device Huawei-Y6-and-Y6-Prime-(2018).md - GitHub

A custom ROM transforms the Huawei Y6 Prime from a sluggish, outdated device into a usable, modern-feeling secondary phone or media player. LineageOS 18.1, in particular, makes it feel like a brand new budget device from 2022–2023.