About Qt translations.

[krab]

It's not correct just to copy qt_ru.qm file. Here ".ts" file ​https://github.com/qt/qttranslations/blob/5.9.0/translations/qt_ru.ts so basically you must have all qm dependencies files in "nls" folder.

Or use "windeployqt" tool, if using windeployqt not an options, here source, example how they combine all dependencies into one qt_ru.qm file ​https://github.com/qt/qttools/blob/dev/src/windeployqt/main.cpp#L934