Looks like there is a bug-change on the Revit installer.
For Information: Revit 2021.1.2 Hot-Fix and InstallLocation - Autodesk Community
Autodesk Revit 2021.1 Hot fix change to Autodesk.RevitAddIns.InstallLocation - Stack Overflow
Maybe InstallPath is now mandatory on Deployment.xml.
Change product installation location | Revit Products 2021 | Autodesk Knowledge Network