I decided to replace MIUI 12.0.3 on my POCO F1 with a custom ROM because the phone will get no further update from Xiaomi. I have written the entire procedure in three parts:

Possible consequences after unlocking

If in future, Google Safety enforces stricter checks, it may flag the phone as insecure. Any application which relies on the Google Safety status may cease to function, see https://news.ycombinator.com/item?id=25025340.

Prerequisites

As at 2021-08-29, there is no form to fill to request for unlock approval from Xiaomi or any waiting period.

Perhaps watch this video https://youtu.be/pByHHTvms4k first to get an idea of the entire process and what you can expect to see at each step. Then the steps below would be easier to follow.

This section is largely adapted from https://github.com/francescotescari/XiaoMiToolV2/issues/23#issuecomment-908811724. The original comment is very well written and apparently works on Ubuntu 20.04.3 LTS.

  • Register on Xiaomi website to get an account and link your device. Your Xiaomi account needs to be older than seven days!
  • Insert a valid SIM card with sufficient internet data bundle, at least 50 MB required during the unlock process
  • Log in to the Xiaomi cloud account on the phone You can do this by going to their site OR even better yet, by signing in directly from Settings > Mi account on your phone. Do this via cellular data connection (not wifi) using your registered SIM number
  • On your phone, go to Settings > About phone and tap 7 times on “Mi version” to enter in “developer” mode, which enables “Developer options” in “Additional settings”.
  • Go the to Additional setting > Developer options and turn on “OEM unlock” as well as “USB debugging”.
  • Now, a very important step which many tutorials fail to even mention: go to “Mi Unlock status”. It should say “Device is locked” and “Phone is safe” if you have never done this before. Tap “Add account and device” and follow the instructions (it will tell you to turn off your wifi connection and turn on your mobile data connection). But here is the catch, even if you have created an account with this phone years ago, it may give you an error (don’t remember exactly what it was). This is what I believe caused the 20031 error, @vmavromatis , because it is exactly what I was experiencing until I found somewhere in the Xiaomi forums that you only need to log out from your phone and log in back again. The problem was that by doing that you are basically creating a new account and I was afraid that could make you wait a long time to get the account authorized. Fortunately I tried it and didn’t have to wait at all. And that was all the prerequisites.

How

The is part one where I resort to using the unofficial XiaoMiToolV2 because I use Fedora 34 Workstation instead of MS Windows which the official unlock app runs on.

  1. Clone XiaoMiToolV2 repo and check out linux branch

     git clone https://github.com/francescotescari/XiaoMiToolV2.git && cd XiaoMiToolV2 && git checkout linux

  2. Edit one Java source file exactly as described https://github.com/francescotescari/XiaoMiToolV2/issues/23#issuecomment-904082515

  3. Install openjdk-11, sudo dnf install java-11-openjdk

  4. Install gradle by following just Step 2, https://docs.gradle.org/current/userguide/installation.html#step_2_unpack_the_distribution. I didn’t bother to set up PATH, etc. described further on the page.

  5. Set up a new Gradle wrapper. This step inevitably overwrites a few Gradle-related files in the repo including gradlew

     # Step above got me gradle-7.2. Adjust this if you've got a newer release.
 /opt/gradle/gradle-7.2/bin/gradle wrapper

  6. Build using the wrapper, ./gradlew build. If this fails, you have probably messed up the Java source code edit.

  7. Run application, sudo ./gradlew run

After clicking on the “unlock bootloader” button in the app, please be patient. My phone showed a static “MIUI” for over 3 minutes which kinda frightened me. But it eventually booted normally into a fresh install (like factory reset) and showed the “unlocked” status under Developer Options.