@aimar Yes, GMT + 8, and notably, that linked site confirms that it indeed resets at midnight in China, not some other time of day. Useful!
There's an excellent post to help install on Redmi Note 9 Pro and similar devices. While of course there will be differences for yours, like firmware, I strongly suspect the basics of unlocking will be the same.
The other difference is that the post is from 2024, and it seems clear that Xiaomi has made it harder to unlock. But at least this shows you the process:
https://forums.ubports.com/post/79264