If you have Qt 5 installed or know a liitle C++/Qt you can try to add Fusion style for macOS in qetapp.cpp
Like this :
p, li { white-space: pre-wrap; }
/**
Autodetec Windows style
@param Windows style
*/
#if defined(Q_OS_WIN) && defined(Q_OS_WINCE)
if defined(Q_OS_WIN)
if ((QSysInfo::WindowsVersion >= QSysInfo::WV_VISTA
&& QSysInfo::WindowsVersion < QSysInfo::WV_NT_based))
style = QLatin1String("WindowsVista");
else if ((QSysInfo::WindowsVersion >= QSysInfo::WV_XP
&& QSysInfo::WindowsVersion < QSysInfo::WV_NT_based))
style = QLatin1String("WindowsXP");
else
style = QLatin1String("Windows"); // default styles for Windows
#endif
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