Yes, I know this process is horrible, but there is currently no way around it

Important Notice

This process is cloud based , which means that Xiaomi can change the rules for old devices retroactively It also means that you need a Xiaomi account

Instructions

1. Download the Mi Unlock tool. Older versions will almost certainly not work with Xiaomi's cloud infrastructure, so download the lastest one from Xiaomi's website
2. Sign into your Xiaomi account on the phone
3. Enable developer settings (by pressing "Settings" > "About device" > "OS version" 7 times)
4. Go to "Settings" > "System" > "Developer settings" > "OEM Unlocking" > "Link account"

• This will require you to install a SIM card and disable WiFi

5. Put the phone into fastboot mode by holding "volume -" while it's booting

• It's important to press "volume -" before you press the power button. Otherwise you might boot into "fastboot d ", which is a different thing

6. Sign into your Xiaomi account in the app
7. Press "Unlock"

• The app may require you to wait up to a week before unlocking. This is required and cannot be changed
• The phone has to be mostly online in that time and always have the SIM card installed