Warning
Before we begin with this procedure, I would strongly recommend you to create a backup of your device storage and all your files stored on your device. Moreover, it is advised to follow the steps mentioned in this post very carefully to avoid permanent damage or to brick your device. If anything goes wrong the author or GetDroidTips is not responsible for it.
What is GSI Stands for?
GSI stands for Generic system image which is an Android System image that can be used to replace the current installed Android version with a new one. It is a pure Android with an unmodified Android Open Source Project (AOSP) code. With Android 8.1, Google introduced the project treble support for many devices and now with Android 9.0 Pie, Google finally added the API level 28 to support Generic System Images to all app developers to install and run the latest Android GSIs on a variety of existing Android devices. To know more: Read here
How to Install Lineage OS 18.1 on Moto G8 Plus
To install, as we said, you need to unlock the bootloader and must have a TWRP (to install via a device) or a PC (to install via Fastboot). Yes, there are two methods to install the Lineage OS 18.1 GSI on Moto G8 Plus.
Disclaimer
AOSP GSIs which is still marked as a pre-release. Even on a device that runs Pie GSIs nicely, it’s still possible to get broken media, camera, RIL, or even flat-out no-boot. You are strongly advised to try PHH’s original and then identify/report issues there, before moving onto other GSIs that are based on his work. Please report bugs on the same thread related to the ROM.
We’re at GetDroidTips won’t be responsible for any kind of damage or error that occurs to your handset while or after following this guide. This is a Custom ROM and may contain some of the bugs or stability issues. We can’t recommend you to use this firmware as your daily driver. Proceed at your own risk.
Pre-Requirements:
Note:
A only arm32 – arm avN
A only arm64 – arm64 avN
A/B arm64 – arm64 bvN
A/B arm32 – arm bvN
Download Links:
Install via TWRP Recovery:
This guide is for those users who have installed TWRP recovery on your device. If your device is not supported, you can try the next method to install the custom ROM via GSI build.
- To install via TWRP, you need to factory reset your device using TWRP
- Go into the Wipe option and Swipe to Factory Reset.

- Transfer the GSI build to your Moto G8 Plus using a USB Cable.
- Once you have moved, you can remove your USB cable.
- In your TWRP, tap on the install button –> Change type to Install Image and find the GSI you have moved in the 3rd step.

- Confirm the flash by choosing the system partition
- Once it is done, you can reboot your device and wait for a few minutes to boot up.
Flash via Fastboot
- First, do the factory reset on Moto G8 Plus. There are two methods to do it, follow anyone.
- Factory Reset When Powered On: To install without TWRP, you have to factory reset using your Umdigi A7 Pro factory reset option.

- Factory Reset via Stock Recovery: Reboot your Moto G8 Plus into stock recovery using a button combination or ADB command.
adb reboot recovery
- In your Stock Recovery, navigate using the Volume UP and DOWN button.
- Make sure to extract the downloaded GSI build.
- After resetting the factory ROM, you can now boot your device into bootloader mode using the adb command
adb reboot bootloader. 
- Now open the extracted folder of GSI build, there, now open the command prompt window by holding the SHIFT KEY and Right Mouse click.
- In your command window, enter the command
fastboot erase system
- To flash the system image, enter a command in the following format:
fastboot -u flash system name_of_system.img
- Wait for the image to flash, it could take a few minutes. Once it has been completed, reboot your device either manually via power key or by entering
fastboot reboot and wait for a few minutes to boot up.
We hope that this guide is helpful to you and you have successfully installed the Custom ROM on your Moto G8 Plus handset easily. If in case anything goes wrong or if you have any queries, feel free to ask in the comments below.
Credits to all the developer from XDA forum and 4PDA forum