Maemo 6 "Harmattan" was fully Qt based. And while it said "MeeGo 1.2" on the device, it really was just Maemo 6 with some compatibility stuff to make it act similar to the MeeGo specifications. One difference was for example that MeeGo was going to use RPM packages, whereas Harmattan used dpkg, just like Maemo 5 had. There were also differences in things like the phone stack, the contacts management, sync framework, etc.
Otoh, while it was Qt based, the UI stack was slightly schizophrenic. Nokia developed a set of libraries called "Maemo Touch Framework" internally initially for the platform, but that turned out to be horrible to work with. Meanwhile the Qt guys developed QML/QtQuick. Then, when the N9 was released, Nokia pushed QtQuick as the platform to build applications on - while all the on-device applications and a lot of the tooling was done for MTF.