Reporting Services 2016 to SharePoint 2016 XML with CSOM?

I have Reporting Services 2016 connecting to SharePoint 2016 onPrem.  I'm trying to create a report with distinct values from a list column (in SP2016).  Standard methods in Report Services don't allow a distinct, so searching the internet lead me to use and XML option.

This link lead me to using XML, but I cannot successfully connect to the SharePoint list.  It cannot find the list or invalid format error.

https://blogs.msdn.microsoft.com/sqlforum/2011/04/27/walkthrough-how-to-get-distinct-values-of-a-column-of-a-sharepoint-list-using-sql-server-reporting-services/

I also read that this soap method was being depricated in favor of CSOM, so this link lead me to another method.

https://docs.microsoft.com/en-us/sql/reporting-services/report-data/sharepoint-list-connection-type-ssrs

When I enter the XML data and test, I get "DTD is prohibited in the XML document". 

Can you help me resolve this issue?