Revit 2020 has all Dynamo builds managed by Revit now - there is no updating Dynamo for Revit 2020 outside of Revit 2020’s point releases.
That installer is specifically for testing future work in Sandbox, as noted here: A new way to get Dynamo Sandbox - Dynamo BIM
If you want any Revit interaction, the latest un-bound release of Dynamo for Revit is version 2.0.2, which works with Revit 2017, 2018, and 2019 (but not 2020).