[Walmart Onn Tablets General] b1zk1t.1337:
It was found that this device in particular is vulnerable to a MediaTek exploit that allows access to the boot.img partition without root access. I don't know about the other models, but here is how to gain root access.

I am not responsible for any damage caused to your tablet or any bootloops.

Requirements​

You'll need a Google USB drivers, a USB C cable, a computer (Windows), and your Onn. 10.1" Gen 3 tablet

Download boot.img from this post on your tablet, you'll need it for rooting.

Step 0. Patching the boot.img​

Download the boot.img attached to this post on your tablet and download the APK for Magisk here. Be sure to turn off Play Protect, because it'll mark it as a virus, and it's not a virus.

Once you've installed Magisk, open it and press "install" on the Magisk card. Press "Select and Patch a File" and select the downloaded boot.img. Start the installation and send the file to your computer using bluetooth / ADB. We'll need the patched file in step 2.

Step 1. Unlocking the bootloader​

! WARNING ! This will wipe all data from the tablet. So please back anything up beforehand.

Step 1a. Obtaining Google fastboot drivers​

To obtain fastboot drivers, please download this. This guide assumes you are running Windows.

Once you have that downloaded, unzip it to a safe folder. You'll need this to recognize your tablet with fastboot.

Step 1b. Connecting your device​

Connect your tablet to your PC using USB. Next you want to go to Settings > About Tablet > Build number and hit that 20 or so times until you unlock developer options.

Next, you want to go to Settings > System > Advanced > Developer options. Here you want to tick "OEM Unlocking" and "USB debugging".

Here's where you plug in your tablet to your computer. Download platform-tools from here and extract them to a folder you can easily access in command prompt.

Once you're in command prompt, connect the tablet to a USB port on your computer. If your tablet shows a dialog asking if you should trust the device, hit yes.

On your computer type this:

adb devices

If you see your device proceed to next sub step

Step 1c. Booting into fastboot​

So now that you've got ADB set up, boot into fastboot like this:

adb reboot bootloader

Wait until you see a black screen that says => FASTBOOT or something similar. This is fastboot.

​

Step 1d. Installing drivers (optional if tablet isn't recognized by fastboot)​

You'll need to install fastboot drivers now. If your tablet isn't recognized when you do fastboot devices, follow this guide to install the drivers.

Go to the usb_driver folder that you just extracted in step 1a. You should see android_winusb.inf. Next, press Windows key + X and click on "Device Manager". Find the "Other devices" section and expand. You should see a device named "Android" with a yellow exclaimation mark. Right click it and click "Update driver". After that, browse my computer for drivers, then click "Let me pick from a list" and click Show All Devices. Now click on Have Disk. Next, press browse and locate that inf file mentioned earlier and press open and hit OK.

You may see a few things, but click on "Android Bootloader Interface" and click next. If it says it can't be trusted, click allow. If it says would you like to install, click install. You have successfully installed the drivers. Fastboot should work.

Step 1e. Actually unlocking the bootloader​

THIS STEP WILL WIPE YOUR TABLET! ONLY PROCEED IF YOU HAVE BACKED EVERYTHING UP OR DON'T CARE ABOUT WHAT'S ON THE TABLET.

Now that you've done that, it's time to wipe your device and unlock your bootloader. You should be in fastboot, and Windows should recognize the tablet.

With fastboot type this:

fastboot flashing unlock

This should unlock your bootloader and wipe your system.

Step 2. Flashing boot.img​

Set up your tablet again and repeat steps 0, 1b, and 1c. You also have to reinstall the Magisk APK again.

So now that you're at fastboot, you can finally flash Magisk. Locate the patched boot.img file you copied to your computer and do the following:

fastboot flash boot magisk_patched.img_[random_strings]

where magisk_patched is the location of the patched boot.img.

Once it's done you can reboot the tablet into the main OS. Congratulations! You've rooted your Onn. 10.1" Gen 3 tablet! Open Magisk to finish the setup.