[Redmi Note 8 Pro Guides, News, & Discussion] polfrank:
/*
* I'm not responsible for bricked devices, dead SD cards, thermonuclear war, or you getting fired because the alarm app failed (like it did for me...).
* Please do some research if you have any concerns about features included in the products you find here before flashing it!
* YOU are choosing to make these modifications, and if you point the finger at me for messing up your device, I will laugh at you.
* Your warranty will be void if you tamper with any part of your device / software.
* Same statement for XDA.
*/

UPDATE 2021-02-28

There has lately been discovered a method to flash begonia/begoniain without the need of an authorised Xiaomi account for flashing. Even if one had earlier not implemented the brick protection method (factory preloader + CFW). This means that CFW is not really needed anymore and that many custom roms are moving away from it. So, in case of brick one can follow this detailed guide in order to unbrick without the need for an authorised Xiaomi account for flashing. There is also an explanatory video that may be helpful for some.

UPDATE 2020-02-25

As of 24 Feb 2020 a new method has been found to help RN8p users avoid bricking their devices. It is a preventive measure and NOT a curative, as it cannot help users who haven't already flashed the specific preloader of the engineering ROM version prior to bricking. For more information see the xda thread by @Agent_fabulous.

ORIGINAL POST

I have created this thread in order to share my experience. I have a Redmi Note 8 Pro that was bricked after flashing a wrong boot.img with TWRP. No fastboot, no recovery, no vibration when pressing the power button. The phone was like dead.

The LED turned on when connected to PC with USB cable. The PC recognised the phone for 5 seconds when holding vol+ before connecting the USB cable. It was recognised as "Mediatek USB port " on Device Manager and after 5 seconds, the PC would lose the connection to the device.

It seems that when holding the vol+ button and connecting the phone to the PC with USB cable, the phone enters to DA mode and waits for a signal that is trying to flash the firmware to it. If the signal doesn't come in the first 5 seconds, the device just gets out of DA mode.

MiFlash does not recognise the phone in this state, as this program can be used only for fastboot flashing.

SP Flash tool recognises the device but returns an "ERROR: STATUS_BROM_CMD_FAIL". This is happening because one has to be logged in with an Authorised Service Account simultaneously when trying to flash with SP Flash Tool. If the authorisation passes, the program starts flashing the firmware to the device.

Requirements

1. MiFlashPro (v4.3.1106.23) downloaded on your pc. (It can be found here.)

2. The stock firmware of your device. (Warning! If you have a Chinese device you have to try with the Chinese firmware. Global device with Global firmware etc. Do not try with Global firmware on Chinese device!)

3. An authorised Service Xiaomi Acount.

The Procedure

0. Unzip your device's firmware.

1. Install MiFlashPro.

2. Navigate to (installation_directory)/MiFlashPro/SP_Flash_Tool/mi and run "account_auth.exe" (Run as administrator). In the window that opens, log in with an authorized Xiaomi Account.

3. Navigate to (installation_directory)/MiFlashPro/SP_Flash_Tool nad run "flash_tool.exe". The SP_Flash_Tool interface opens. Now you have to select the 3 files:

Download-Agent: (installation_directory)/MiFlashPro/SP_Flash_Tool/MTK_AllInOne_DA_mt6765_mt6785.bin

Scatter-loading File: You will find this one on your stock rom folder, especially on the folder called "images".

Authentication File: (installation_directory)/MiFlashPro/SP_Flash_Tool/auth_sv5.auth

4. Press the "Download" button.

5. Connect the USB cable to your PC but NOT YET to your phone.

6. Hold the vol+ button on your phone pressed and NOW connect the cable to it.

7. The program should now react and start the flashing process without giving an error.

8. Wait for the flashing process to end and enjoy!

Sidenote

You surely wonder where you can find an authorised Xiaomi account.

There are rumors that there are people who connect to your PC with remote-desktop programs and provide the log-in details just when they are needed during the flash process. And they get paid for it (~10-15 USD, maybe more).

Another solution would be some mobile-phone technician in you city. He/She may have an authorised account for fixing the phones locally at the store.

You may also be lucky to have a friend with an authorised account.

But I do not know of a valid way to get an authorised account for yourself at the time and age of writing.

Sidenote 2

If I remember correctly, on an older Xiaomi MTK phone, they managed to bypass the authorisation by using a modified DA file. If you don't want to pay for an authorisation service, you can wait for a while. But it is unknown if/when such a file is going to be released for Redmi Note 8 Pro.