An object-oriented and type-safe programming language that has its roots in the C family of languages and includes support for component-oriented programming.
The question is invalid, because the actual responsibilities of Telerik are to support Microsoft platforms such as .NET 5, not the other way around.
Telerik announced its .NET 5 support last year, https://www.telerik.com/blogs/dotnet-conf-2020-telerik-ui-for-winforms-wpf-officially-supports-dotnet-5 but there can be quite a few gaps/limitation due to Microsoft's unfinished business on .NET Core WinForms designer and so on.
VS2022 and .NET 6 are coming, so hopefully you get better experience later this year.