It also looks like QT is available LGPL.
Yes, it is, as stated in https://www1.qt.io/qt-licensing-terms/.
In case of dynamic linking, it is possible, but not mandatory, to keep application source code proprietary as long as it is “work that uses the library” – typically achieved via dynamic linking of the library. In case of static linking of the library, the application itself may no longer be “work that uses the library” and thus become subject to LGPL. It is recommended to either link dynamically, or provide the application source code to the user under LGPL.
As long as the library is dynamically linked to the appliction (parts of Lumina) and the source code of the library is provided, there should be no problem.
Complete corresponding source code of the library used with the application or the device built using LGPL, including all modifications to the library, should be delivered with the application (or alternatively provide a written offer with instructions on how to get the source code). It should be noted that the complete corresponding source code has to be delivered even if the library has not been modified at all.
The code can even be created/changed using Qt Creator without any hassle.