Python code to get print layout extents as a layer in qgis map

print_layout_extents_to_map.py

def getCompositionExtents(crsCode=2154) :
    
    # layer
    vl = QgsVectorLayer("Polygon?crs=EPSG:%s"%(crsCode), "Extent Polygons", "memory")

    # defining CRS
    crs = vl.crs()
    crs.createFromId(crsCode)
    vl.setCrs(crs)
    
    # data provider
    pr = vl.dataProvider()

    # start editing
    vl.startEditing()
    
    # add attributes
    vl.addAttribute(QgsField("name", QVariant.String))

    # get compositions
    projectInstance= QgsProject.instance()
    projectLayoutManager = projectInstance.layoutManager()
    comps = projectLayoutManager.printLayouts()

    # iterate over compositions
    feats = list()
    for comp in comps :
        nom = comp.name()
        print(nom)
        for item in comp.items() :
            if (isinstance(item, QgsLayoutItemMap)) :
                print("toto")
                print(item)
                e = item.extent()
                feat = QgsFeature()
                feat.setGeometry(QgsGeometry.fromRect(e))
                feat.initAttributes(1)
                feat.setAttribute(0, QVariant(nom))
                feats.append(feat)

    # add features
    pr.addFeatures(feats)

    # commit changes
    vl.commitChanges()
    
    return(vl)
    
def addLayerToCanvas(vl) :
    # add layer to canvas
    QgsProject.instance().addMapLayer(vl, False)
    layerTree = iface.layerTreeCanvasBridge().rootGroup()
    layerTree.insertChildNode(-1, QgsLayerTreeLayer(vl))
    
    
vl = getCompositionExtents() # create layer from extents
addLayerToCanvas(vl) # add layer to canvas
#writer = QgsVectorFileWriter( "output_path_and_name.shp", vl.encoding(), vl.fields(), QGis.WKBPolygon, vl.crs() )