ok so i read the code and kept chasing and figured a way to make it happen. so a number of formats can be published with just .publish() but some apparently need to be analyzed??? but the product of a analyze on a geopackage is broken. you tell it you are analyzing a geoPackage but it returns that its CSV. so then you have to sternly say that no it is in fact geopackage. so this works ...
analyzed = agolSpace.content.analyze(item = sourceItem, file_type='geoPackage')
publish_parameters = analyzed['publishParameters']
publish_parameters['type'] = 'GeoPackage'
item = sourceItem.publish(publish_parameters, file_type='GeoPackage')