From Esri resource center: "As of ArcGIS Enterprise 10.6.1, web apps can be shared to collaboration participants using a version of ArcGIS Enterprise that is equal to or greater than the sender. Web apps can be shared from ArcGIS Enterprise to ArcGIS Online, however it is not possible to share web apps from ArcGIS Online to ArcGIS Enterprise."
Is it in the product plan to allow sharing of web apps from AGOL to Enterprise? I recently stood up a Portal site and am trying to migrate content from my old AGOL site to the new Portal via distributed collaboration. I know I can use AGO Assistant as a workaround to copy content, but then I end up having to rebuild links, etc in the apps so I was hoping to streamline the process using distributed collaboration.