With the release of Sitefinity 14.1, we have deprecated the support for WebForms for front-end development (Built-in WebForms Widgets, WebForms Widget templates, Hybrid Page templates, Responsive design module)
Sitefinity customers can use one of these two alternatives:
Sitefinity’s MVC implementation is fully aligned with Microsoft’s and existing MVC code works ‘as in’ in Sitefinity.
Learn more about .NET Core support in Sitefinity and how .NET Core compares to .NET MVC