On Mac,

the return values of QLocale::uiLanguages() normally like:
("en", "zh-Hans", "zh-Hant", "nb", "ja", "fr", "de", "es", "it", "pt", "pt-PT", "nl", "sv", "da", "fi", "ru", "pl", "ko", "ar", "cs", "hu", "tr", "th", "ca", "hr", "el", "he", "ro", "sk", "uk")

and obviously "zh-Hans", "zh-Hant" are "zh_CN", "zh_TW" in Qt world. and they can't be used to construct a QLocale.

Test code:

QLocale cl1("zh-Hans");
qDebug() << cl1.name();
QLocale cl2("zh-Hant");
qDebug() << cl2.name();

return value:

"zh_CN" 
"zh_HK"

it should be following normally:

"zh_CN" 
"zh_TW"

I mean normally the default locale for Traditional Chinese should be zh_TW(Taiwan), they have more users than zh_HK(Hong Kong).