I used the new Vector Tile Style Editor to modify a basemap and saved that newly modified basemap. Upon saving, I now see the modified basemap in My Content of my ArcGIS Online account, however, I cannot figure out how to pull the modified basemap into my Company's Portal for use in webmaps. How do I go about adding a custom basemap to a Portal?
I just got off the phone with tech support and I tried a myriad of different ways to get styles into Portal. It looks like it's not officially supported. Along with the ESRI tech support, we published the Pro document out to portal as a vector tile layer, copied the hosted item, and then tried to update the style.
I brought the root.json from AGOL and tried changing a few URLs to our portal URL and we got nowhere. I think a lot of organizations are dead in the water if they can't get their styles into Portal or on ArcGIS Server.
I went through the recomended workflow from the comments and was able to get my custom vector style into my 10.5.1 portal.