Thanks @wally for your information.
I said 30 days, because apart from the 168 hour thing, one must have a Xiaomi account more than 30 days old. Which currently I had not.
I just bought it. Hope it works. I do not want to be stuck on Android.
With your information I kept searching and found that lots of people complain from no receiving the sms code. It seems a random issue between countries, attempts and the xiaomi unlock app version.
In this XDA forum, the last post is dated Apr 15, 2026 and a guy from Canada, finally, got the SMS. Hope you also are lucky this time.