Application runs without running
I tried to use GNOME Builder to build and run gnome-calendar. It did not work as expected. The build succeeded and the build part seem to be fine however running the application does not work. When clicking the run button on the IDE the console runs the application and process managers like htop can see the app running but there is no window generated so the application does not really run. I tried to run the app by terminal directly but it complains of missing dependencies. I suppose GNOME Builder uses flatpak to build and run the debug app.
Is this expected behaviour? If so how are we supposed to debug GUI apps without a window to open?