Add column.isSortable & childComponents.sortIcon

column.isSortable - disable sorting for specific column
childComponents.sortIcon - gives ability to customize sortIcon component

  columns: [{
      ...
      isSortable: false,
      ...
    }],
  childComponents={{
        sortIcon: {
           ...
        }
  }}

Demo: https://komarovalexander.github.io/ka-table/#/sorting
Docs: http://ka-table.com/docs_props.html#toc1