PyQt5. QListWidgetItem в QListWidget. отслеживать правую кнопку мыши

вы можете устанавливает фильтр событий на объект list_widget.

from PyQt5 import QtCore, QtWidgets

class Widget(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(Widget, self).__init__(parent)
        
        self.list_widget = QtWidgets.QListWidget()
        self.list_widget.installEventFilter(self)
        
        btn = QtWidgets.QPushButton("add")
        btn.clicked.connect(self.add_item)

        grid = QtWidgets.QGridLayout(self)
        grid.addWidget(self.list_widget, 0, 0)
        grid.addWidget(btn, 1, 0)

    def eventFilter(self, obj, event):
        if obj is self.list_widget and event.type() == QtCore.QEvent.ContextMenu: 
            item = self.list_widget.currentItem()
            if item:
                text = item.text()
                print(f'clicked item text: {text}')
       
        return super().eventFilter(obj, event)

    @QtCore.pyqtSlot()
    def add_item(self):
        num = self.list_widget.count()
        self.list_widget.addItem(f"item {num}")


if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    w = Widget()
    w.show()
    sys.exit(app.exec_())