Hello Lev:
I've been using Pro 2.0.1 now and I ran into the same question as you did. I saw this thread and I came up with a solution, though it might not suit for every cases, but it is still a solution!
The idea is that inside the arcpy.mp layer class(the class you use Map.listLayers()[0] to get) there's a property called symbology. It has read and write access. So what you can do is to pre-set a symbology lyrx file and add it as layer class into map class, then extract it's symbology as a variable. Then you remove this symbology layer, add the layer you really want, assign the symbology variable as the new value for the layer's symbology property. Then you save it and export images.
Here is my code:
output_aprx = arcpy.mp.ArcGISProject(output_aprx_pth)# read it as object using arcpy, then to modify it
#Working on converting input feature class to a layer inside aprx project file
Map = output_aprx.listMaps("Map")[0]
Layout = output_aprx.listLayouts()[0]
title = Layout.listElements("TEXT_ELEMENT")[0]# Get the title object
title.text = "DC "+ outname# Change the text message of title to what we want
if symbology == 0:
Map.addLayer(input_lyrF, "TOP")
else:
sym_lyrF = arcpy.mp.LayerFile(symbology)
Map.addLayer(sym_lyrF, "TOP")
sym_layer = Map.listLayers()[0]
sym_obj = sym_layer.symbology
Map.removeLayer(sym_layer)
Map.addLayer(input_lyrF)
input_layer = Map.listLayers()[0]
input_layer.symbology = sym_obj
output_aprx.save()# Save the edits
Layout.exportToJPEG(outmaps_path + name_element + ".jpg", resolution = out_resolution)
I tried it on simple symbol and graduate color, everything works fine.
