[Xiaomi Mi A2 / 6X Guides, News, & Discussion] Andres Videla:
Clarifications:

No matter the version of Android that our Smartphone has, the procedure is the same.

When unlocking the bootloadrer all our personal data and applications of the smartphone will be erased, I recommend making a backup of our personal files.

Requirements:

We will obviously need our Xiaomi Mi A2 and have a PC.

Steps:

1-Preparing the smartphone

Enable oem debugging and usb debugging:

Open Setting> System> About Phone> Press where it says "Buil Number" until you enable the developer options. Let's go back a step, and we will see that within the options of "System" a new one will appear, called "Developer options"; we enter it, and within the options we have to enable "OEM unlocking" and "USB debugging".

Then we will proceed to turn off our smartphone.

Once turned off, we will press at the same time volume - and power for about 5 seconds, until our cell phone turns on (this in order to enter the fastboot mode), if everything was done correctly, the following image will appear on your screen.

[IMG="Fastboot Image"]https://3.bp.blogspot.com/-Y2BqHFOb9lU/W3nVGX9p0wI/AAAAAAAAAPw/055pOQfk7bwbTyVb0qPc2FwtRCxpLndeACLcBGAs/s320/fastboot.png[/IMG]

We connect the cell phone to the PC

2-Preparing the PC

Install Drivers

For me the best way to install the drivers is as follows (if you know a better way I accept suggestions)

Download the tool My Unlock

Extract the zip file into a new folder on our pc, double click to execute the file called "miflash_unlock", we will open the application, top right of it will be the "wheel" of settings , we click on it to enter; a new window is displayed, and where it says "My Usb Driver" we click on "Check"; a "Connect your device again" notice will appear, we disconnect and connect our cell phone to the PC again, and we will have the driver installed.

We can close, we do not need this app anymore

Install the adb tools on the PC

Download the installer

1. Run it (Require administrator privileges)

2. Press Y / Yes to install ADB and Fastboot or N / No to skip

3. Press Y / Yes to install ADB system-wide or N / No for current user only

4. Press Y / Yes to install Drivers or N / No to skip

5. Continue Driver installation

6. 15 seconds passed - finished!

3-Finally we will proceed to unlock the bootloader

Download the following folder "UNLOCK BOOTLOADER XIAOMI MI A2"

We enter in it, we will find a .bat file called "unlock auto" (we make sure to have our smartphone connected to the PC in fastboot mode) we double click to execute it.

Immediately on our cell phone will appear a warning on the screen about which we are going to unblock the bootloader. And pressing twice volume -, select the option "unlock the bootloader", then press the button "power" and our smartphone will restart a couple of times, all our information will be erased and we will have the bootloader unlocked.

Suggestion:

Once the bootloader is unlocked, I advise you to turn off your smartphone again and enter fastboot mode again, go back to the "UNLOCK BOOTLOADER XIAOMI MI A2" folder and double-click the .bat file called "flash unlock critical", this with the purpose, that when we want to restore our smartphone and flash the stock firmware we have no problems.

Here I leave a video on YouTube that is a visual guide to the procedure.