[Walmart Onn Tablets General] diplomatic:
TWRP Custom Recovery for the Onn Android Tablet series

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This is the first fully-featured custom recovery for Walmart's MediaTek-based Onn tablets: ONA19TB002, ONA19TB003 and ONA19TB007. TWRP needs no introduction. If you have come here, you probably have some idea of what it is and what it's used for. This TWRP build does not need the bootloader unlocked or VBMeta verification disabled, although it's recommended that you at least unlock the bootloader.

DISCLAIMER

Everything described in this thread is done at your own risk. No one else will be responsible for any data loss, corruption or damage of your device, including that which results from bugs in this software.

FEATURES

Decrypted data partition

All USB modes functional: MTP, ADB, Mass Storage, OTG, Charging

Fast boot time

Adoptable storage mounting

Firmware image backup and restore

Works under locked bootloader

Android 9 build fits within the 16MB recovery partition -- no compromises or partition resizing necessary

INSTALLATION METHOD 1

Download the recovery to your PC and unzip the image

Unlock the bootloader (skip if you have already done this)

Enable OEM Unlock in Developer Options in Android Settings

Boot into fastboot mode either by holding vol. up+power to power it on and selecting "Fastboot mode", or by running the 'adb reboot bootloader' command from within Android.

Install fastboot and appropriate drivers on your PC if you have not set those up

Unlock the bootloader with the command

fastboot flashing unlock

...and follow the instructions on the screen.

This will wipe your data.

Flash the custom recovery with

fastboot flash recovery twrp-3.3.1-ONA19TB002.img

(use the right file name path for your device)

Reboot to recovery with

fastboot oem reboot-recovery

INSTALLATION METHOD 2

This assumes you are familiar with SP Flash Tool or can figure it out on your own

Download the recovery to your PC and unzip the image

Get the appropriate scatter file for your device. The scatter file may be found in the device's firmware under /system/data/misc.

Set up SPFT Download tab as Download Only. Load your scatter file.

Under the recovery line, double-click Location and open your TWRP image.

Click Download and connect your powered-off tablet to your PC. SPFT will automatically flash the recovery to the emmc and disconnect when finished.

INSTALLATION METHOD 3

Head over to Amazing Temp Root for MediaTek ARMv8, read the requirements and directions, and grab the latest mtk-su.

Open a root shell with mtk-su

Flash the (unzipped) recovery with the command:

dd bs=1048576 if=twrp-3.3.1-0-ONA19TB002.img of=/dev/block/by-name/recovery

(replace the if= file name with your appropriate recovery image path)

Exit root shell

START RECOVERY

Three methods:

On a powered off tablet, hold Vol. up+power for about 3 seconds. In the menu that appears, select "Recovery mode"

With Android ADB, use the command 'adb reboot recovery'

From Android root shell, use the command 'reboot recovery' or just use any root app with OS reboot features

NOTES

Kind of important: Make a backup of your Crypto Footer as soon as you can. This is the encryption key to your data partition. When accessed from TWRP, this key can get "upgraded" so that you will get locked out of Android. TWRP uses a hacky workaround that saves and restores the original footer on every /data decrypt. But that method is not what I would call 100% reliable.

Make sure you have a backup of the untouched stock system and vendor images. There are no official firmware packages available to download.

Only mount system/vendor partitions in read/write mode if you have unlocked the bootloader. It is recommended to choose to leave system read-only at the startup prompt unless you have a specific reason to modify it. If the bootloader is locked, then dm-verity is enforced.* So merely mounting it once in r/w will cause a boot loop.

It's currently not possible to install incremental OTA updates using this TWRP. Use the stock recovery to update the FW. That will only work if you have never mounted system/vendor in write mode.

DOWNLOAD (Nov. 30, 2019)

Current version: 3.3.1-1

ONA19TB002 - Onn 8" model

ONA19TB003 - Onn 10.1" model

ONA19TB007 - Onn 10.1" w/keyboard model

Source code

ONA19TB002 | ONA19TB003 | ONA19TB007

ACKNOWLEDGEMENTS

The team behind TWRP & OmniROM

[MENTION=8491352]tek3195[/MENTION] for testing and feedback on the 8" model