No QtQuick3d [1] was from the beginning GPLv3 only (It is not even released yet, but Qt 5.14 release is tommorow). It is a bit awkward because now there are competing 3d engines inside one toolkit.
What I did write was that they switched their licensing default for most new modules from LGPL to GPL. So unlike Qt Quick (the original 2D Qt Quick) which was started under Nokia and licensed LGPL (or commercial)… the new Qt Quick 3D (*) was never licensed under LGPL but is licensed only under GPLv3 (or commercial).
[1] https://doc-snapshots.qt.io/qt5-5.14/qtquick3d-index.html