Revit 2021, the GenerativeDesignRevit package is under C:\ProgramData\Autodesk\RVT 2021\Dynamo\2.5\packages.
In DY, the path are:
C:\Users\yingx\AppData\Roaming\Dynamo\Dynamo Revit\2.5
C:\ProgramData\Autodesk\RVT 2021\Dynamo\2.5\packages
but there us no such package in the side package / node menu.