Start Windows under VirtualBox under Ubuntu
Start the Qt SDK's Qt Creator (starting the 'plain' Qt Creator will not be successfull)
Create a new project (screenshot (png))
Choose 'Mobile Application' (screenshot (png))
Choose a folder to save the application (screenshot (png))
Select all environment types (screenshot (png))
Create a Dialog called 'Dialog' (screenshot (png))
Skip the version control management system (unless you really want to have a version control system)(screenshot (png))
The form designer is shown (screenshot (png))
From the widget toolbar, drag a QPushButton on the form (screenshot (png))
Right-click on the QPushButton and left-click 'Change text' (screenshot (png)) and change the text to 'Press me'
Right-click on the QPushButton and left-click 'Go to slot' (screenshot (png))
Select 'clicked()' (screenshot (png))
The code editor is started (screenshot (png))
Add the following line of code (screenshot (png))
In the 'Project Settings' select the Symbian device (screenshot (png))
Run the application by clicking on 'Run' (screenshot (png))
The application is started. If you have no mobile phone connected, 'You have no device plugged in' will be displayed in the 'Application Output' (screenshot (png)). A Symbian executable, however, is already produced!
To nevertheless test the application, change the 'Project Settings' to 'Qt Simulator' (screenshot (png)). Click 'Run'
The application is shown in the Qt Simulator (screenshot (png))

(C++) 'Hello Qt' using Qt Creator under Windows under VirtualBox under Ubuntu for Symbian