I faced the same problem.
I managed to unbrick the device by using the chinese v5.1516.00 of SP Flash Tool that you can download here:
https://www.mediafire.com/?tpjg4jtdf7sj40t.
So I am reading a lot of people online are facing the same problem I am unable to solve.
My mi account is successfully connected to not one but two phone numbers, I have logged in on desktop and also used "find my phone".
I have tried both with latest stable and developer rom, on Windows adb...