Hi,
After you installed the Qt bundle, did you make sure that the paths to the binary qmake,etc are accessible , ie, open a terminal and try running the qmake command. If you get the same error, then you need to specify the path to the Qt binary.
Have you installed it in the default directory - /usr/lib/x86_64-linux-gnu/qt5/bin/?
It looks like you've installed it in the directory for the altera tools.
Have a look at this link
https://www.digitalsolutionslab.com/qt-designer-installation-and-configuration-for-the-de1-soc-control-panel-part-3-of-4/ It has instructions for installing the Altera tools and Qt on Linux systems. It maybe different for Ubuntu, but you will still need to perform the QtCreator steps. Once this is done , the control panel will start up .