I wanted to install a custom rom on my Xiaomi Mi A3, so I had to install the twrp. I enabled oem unlock from the developer settings of the phone and rebooted into bootloader mode, but when I ran the command "fastboot oem unlock" it gave me as a result
FAILED (remote: 'unknown command')
fastboot: error: Command failed
(this on linux)
Then I tried on windows, but fastboot did not recognize my device, while windows and adb yes. Any solution?
On
As Guerlando OCs said, you will need to use Xiaomi's unlock tool to unlock your Xiaomi device (Windows only). Also, you can use XiaoMiTool V2 if you are on Mac or Linux (on Windows will also work).
fastboot oem unlock will not work, because OEMs set their own fastboot oem commands. Xiaomi unlock tool uses a modified version of fastboot which adds a command: fastboot flashing unlock_bootloader [UNLOCK_CODE], that unlocks the bootloader of the device after obtaining the code from Xiaomi's servers.
If you need to install drivers, download MiFlash from here and install the device drivers from there.
You have to use Xiaomi's unlock tool, not fastboot. After 7 days you'll be able to unlock. If your xiaomi is not recognized on windows, download an older xiaomi unlock tool (on their website there are lots on the faq), it will have a driver installer, then your xiaomi is going to get recognized so you can unlock.