The Kendo UI Grid's pager for UI for ASP.NET Core does not have an "All" option and it can't be configured in the Razor syntax.
Using the Kendo UI Grid's pageable.PageSizes, the ALL option is not available for UI for ASP.NET Core as it's only an Int32[].
The All option should be included like in the UI for ASP.NET MVC Razor Syntax.