When a web map containing only Open Geospatial Consortium (OGC) Web Map Services (WMS) is used to create a story map using newer version of the story map template, the error message "This web map doesn’t have any ArcGIS layer" is returned.
This is a web security issue with a specific WMS service, not an issue with OGC WMS services. When an ArcGIS server is configured to not allow cross-origin use of its services, the developer's console shows errors relating to 'Access-Control-Allow-Origin' CORS policy.
Any WMS services coming from servers without this CORS restriction work as expected in StoryMaps. See this service as an example: https://ows.terrestris.de/osm/service