Alright, I found that all is caused by localizedStringWithFormat:. in iOS 14, it would add U+2068 and U+2069 (unicode FSI) around "5.6k". So the text's direction was decided by the Arabic part. This is a new feature of localizedStringWithFormat: in iOS 14.

@Claude31  Firstly, at the Localizable.strings file add the following line: "%@_fans" = "%@ متابعين"; And then create string like this: NSString *num = @"5.6k"; NSString *str = [NSString localizedStringWithFormat:NSLocalizedString(@"%@_fans", nil), num]; label.text = str; It will show different result between iOS 13 and iOS 14, both simulator and device