Telerik UI for WPF comes with .NET Core support. There is a set of dlls built against the .NET Core framework which you can reference in an application and start using the Telerik controls. See how to migrate your app in the Migrаting to .NET Core article.
Note that since R2 2020, Telerik UI for WPF supports also .NET 5.0 Preview.
To work with the Telerik .NET Core dlls you will need to have the following installed.
The latest .NET Core 3.1 SDK.
Visual Studio 2019 version with the latest update. The minimum version of Visual Studio is v16.4.
Read more about the .NET Core requirements in the Prerequisites for .NET Core on Windows MSDN article.
The Telerik controls can be drag/dropped from the Visual Studio Toolbox. To enable this under .NET Core you will need to reference the Telerik dlls via nuget. Installing the nuget packages will add the corresponding controls in the toolbox. Drag and drop from the toolbox is available only for the projects that have the Telerik nuget packages installed.
Additionally, the Telerik controls introduce customized design-time support as using smart tags, design-time selection, and also the standard control properties changing through the Visual Studio Designer
Creating a project via the Telerik Visual Studio Extensions, allows you to select a NuGet version and automatically add the packages in the project when created, thus adding the Telerik .NET Core controls into the Visual Studio Toolbox.