Xiaomi Mi A2

https://en.wikipedia.org/wiki/Xiaomi_Mi_A2

Flash Xiaomi Mi A2 Android ROM.

A system with Windows operating system will be needed.

Device needs enough power for this process.

Back up data before proceeding.

All user data will be purged in this process.

Unlock

Configure bootloader in flashboot mode to flash a flashboot image.

Procedure is similar for different Android versions.

Data and applications can be erased, Make backup.

Developer mode

To enable developer mode:

Settings » About Phone » Build Number or Version » Tap seven times

Message appears shortly "You are now a developer!".

USB debugging

Enable USB debugging:

Settings » System » Advanced » Developer options » USB debugging » Enable

OEM unlocking

Enable OEM unlocking:

Settings » System » Developer options » OEM unlocking » Enable

Or via command line.

On Windows computer download and extract Xiaomi Flash Tool.

Connect smartphone with USB cable to Windows computer.

From extracted Xiaomi Flash Tool folder "...\MiFlash20210226\Source\ThirdParty\Google\Android" or use alternative ( see https://www.xda-developers.com/install-adb-windows-macos-linux ) and after using "Open in Windows Terminal" enter:

adb devices

On smartphone message "Allow USB debugging?" appears and select "Always allow from this computer" and "ALLOW".

On computer "List of devices attached" shows device.

Reboot in fastboot:

adb reboot bootloader

or turn off our smartphone. Once turned off, press at the same time volume - and power for about 5 seconds, until our smartphone turns on FASTBOOT appears on screen. Ones in fastboot mode use in same Windows Terminal as before and enter:

.\fastboot devices

If device is listed, enter:

.\fastboot flashing unlock

On smartphone confirm by selecting "Yes". When process completes, enter:

.\fastboot flashing unlock_critical

When process completes, reboot smartphone normal by typing:

.\fastboot reboot

Sources:

https://doc.e.foundation/pages/enable-usb-debugging

https://forum.xda-developers.com/t/guide-how-to-unlock-bootloader-xiaomi-mi-a2.3831484/

Fastboot info:

https://helpmanual.io/help/fastboot/

Fastboot image

Download and extract a fastboot image from a site like following.

For older fastboot images: https://forum.xda-developers.com/t/fastboot-jasmine-xiaomi-mi-a2-fastboot-images.3824849/.

For recent fastboot image: https://c.mi.com/oc/miuidownload/detail?guide=2.

Flash tool

Download and extract Xiaomi Flash Tool.

Use XiaoMiFlash from extracted files and select folder with extracted fastboot image.

Boot smartphone in fastboot mode.

Select "clean all" and "refresh". When device is listed, select "flash".