@Rajoli Hari Krishna - Thanks for the question and using MS Q&A platform.
Based on the provided information, it seems that you have already enabled the private endpoint for the Data Factory resource type and successfully copied data from Standard subscription to Enterprise Scale subscription storage accounts with the Azure Self-hosted integration Runtime.
Regarding your question about connecting to ADF from the Azure App service using App Service Managed Identity, it depends on your specific scenario. If you want to access the ADF portal from the App service using Managed Identity, then you would need to create a private endpoint for the "portal.adf.azure.com" sub-resource. However, if you are only using the Managed Identity to access the ADF APIs or perform data integration tasks, then you may not need to create a private endpoint for the portal sub-resource.
In general, private endpoints are used to securely access Azure services over a private connection. If you want to access the ADF portal securely from your App service, then creating a private endpoint for the portal sub-resource would be a good option. However, if you only need to access the ADF APIs or perform data integration tasks, then you may not need to create a private endpoint for the portal sub-resource.
Hope this helps. Do let us know if you any further queries.
If this answers your query, do click Accept Answer
and Yes
for was this answer helpful. And, if you have any further query do let us know.