1. Create Windows Forms App
2. Select Target Framework .NET Core 3.1, 5.0 or 6.0
3. Convert to Telerik Controls via the WinForms Extensions menu

You will see that you cannot select version .NET Core 3.1, 5.0 or 6.0 from the drop-down.

If you attempt to convert the project by selecting version 2.0 or 4.0 the Visual Studio will crash.