I had the same request , i.e. the need for a standalone version of the Ranorex Report Viwer and contacted the Support a couple of days ago.
They sent me the most recent version of a stand-alone Report Viewer:
But this tool is not officially supported nor maintained.
It still works with Ranorex Studio 9.3.1, but doesn't support the latest features like playing the videos from the report.
People from Ranorex have the development of an official version in their backlog.
Hope this helps,
Ask general questions here.