unfortunately nothing happens when I click in the label
Sounds like the model is intercepting these signals and is eating them. The only other thing I can suggest is adding an event filter on the combobox to look for mouse press events (or better mouse press / release pairs), but then that gets ugly because you'd have to deal with the open / closed state of the drop-down, and if open, determining from a pixel mouse position which specific item was clicked.

Unlike QAbstractItemView, the combobox does not have any concept of a QItemSelectionModel (or at least it doesn't expose this in the public interface) so there is no way to interact with the selection state.