Maybe the plugin itself can't be found.
To debug further set the QT_DEBUG_PLUGINS environment variable to 1, this should give you some output on what the Qt plugin loader does.
See https://doc.qt.io/qt-5/deployment-pl...ugging-plugins
Or try a different SQL plugin, e.g. for SQLite, just to see if that can be loaded and only the one for MySQL cannot.
Cheers,
_
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