I did that a few years ago. Had to download some tool to my PC.

Then make a request that takes 2 weeks to go through. and enter the or whatever (this was like 2016 or something).

Whole process was clearly designed to make you give up.

Their phones where junk then though and i just got something else in the end. They're a lot better now so actually unlocking it is probably worth something now.

When you say junk then, I find that interesting as my first was a Redmi Note 4 launched in 2016, that I got in 2017 (and did this unlock process on, as I bought it in China), and the reason I got that phone in particular was its price (in the UK it was £120, in China I got it slightly cheaper at 1100 CNY) and that it was actually the fastest Android phone available at the time according to the AnTuTu benchmarks.

The modern Redmi Note series is usually a generation behind on performance now, but I keep buying them as they're still faster than I need and there's always still a decent phone less than £150. Only complaint is with the camera, which never seems to get any better even when they claim to have upgraded it.

The two week process was to irritate resellers who change the phone to target markets it wasn't designed for.