Hi,
If you have an ArcGIS Enterprise base deployment (Server federated with a Portal) you can publish the data in bulk: https://enterprise.arcgis.com/en/portal/latest/use/bulk-publish-arcgis-server-feature-layers.htm.
This will create a service endpoint and a portal item for every single Feature Class/Table accessible thru the registered enterprise geodatabase connection.
If an enterprise geodatabase data contain the standard metadata (hopefully), this will be also published along with the portal item metadata.
Moreover, data and metadata updates are automatically accessible thru the published services/portal items.
Then, you can setup a collaboration between the ArcGIS Enterprise and ArcGIS Online: https://enterprise.arcgis.com/en/portal/latest/administer/windows/set-up-an-arcgis-enterprise-and-ar....
The collaboration will transfer selected portal items with its metadata to ArcGIS Online and also sync any updates which might happen on the Enterprise side.
Lastly, the service endpoints (REST API) of data published in the Enterprise has to be publicly accessible on the Internet, to be available to ArcGIS Hub as a downloadable data.
Matej