Currently there is no way to pass custom rendering component into header template (in jQuery version there was headerTemplate). For example, you are exposing headerSelection prop, but what if I want to render fancy Material UI checkbox there. Currently I do not have ability to do that with native react flow.
The feature is available in version 1.3: https://www.telerik.com/kendo-react-ui/components/grid/api/GridProps/#toc-headercellrender