[Regr: 5.x -> 6.x] QTranslator loads zh instead of zh_TW translation

My app has two Chinese translations: Chinese (China) and Chinese (Taiwan). Translation files are named app_zh.qm and app_zh_TW.qm accordingly.

When I try to load Chinese (Taiwan) translation, Qt 6.x loads Chinese (China) instead. Qt 5.12.12 works fine.

Code I use:

QTranslator t;
t.load(QLocale("zh_TW"), "app", "_", path);

QTranslator::load succeeds and loads QLocale("zh") translation instead of QLocale("zh_TW").