DataTable: non-standard server-side

HTML

<script src="//cdn.datatables.net/1.10.11/js/jquery.dataTables.min.js"></script>
<link rel="stylesheet" href="//cdn.datatables.net/1.10.11/css/jquery.dataTables.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.12.0/moment-with-locales.min.js"></script>
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>DataTables Example</title>

  <!-- jQuery -->
  <script src="https://code.jquery.com/jquery-3.7.1.min.js"></script>
  
  <!-- DataTables CSS -->
  <link rel="stylesheet" href="https://cdn.datatables.net/2.1.5/css/dataTables.dataTables.css" />
  
  <!-- DataTables JS -->
  <script src="https://cdn.datatables.net/2.1.5/js/dataTables.js"></script>
  
  <!-- DataTables Buttons CSS -->
  <link rel="stylesheet" type="text/css" href="https://cdn.datatables.net/buttons/2.3.4/css/buttons.dataTables.min.css">
  
  <!-- DataTables Buttons JS -->
  <script src="https://cdn.datatables.net/buttons/3.0.0/js/dataTables.buttons.min.js"></script>
  
  <!-- Buttons JS (for Excel and PDF) -->
  <script src="https://cdnjs.cloudflare.com/ajax/libs/jszip/3.2.2/jszip.min.js"></script>
  <script src="https://cdn.datatables.net/buttons/3.1.2/js/buttons.html5.min.js"></script>
  <script src="https://cdn.datatables.net/buttons/3.1.2/js/buttons.print.min.js"></script>

  <!-- FontAwesome for icons -->
  <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.0.0-beta3/css/all.min.css">
</head>
  <body>
    <div class="container">
      <table id="example" class="table table-bordered table-small-font table-striped table-hover dt-responsive" cellspacing="0" width="100%">
        <thead>
          <tr>
            <th>Name</th>
            <th>Language</th>
          </tr>
        </thead>

        
      </table>
      
    </div>
  </body>
</html>

CSS

body {
  font: 90%/1.45em "Helvetica Neue", HelveticaNeue, Verdana, Arial, Helvetica, sans-serif;
  margin: 0;
  padding: 0;
  color: #333;
  background-color: #fff;
}

JavaScript

var table = $("#example").DataTable({
  "bLengthChange": true,
  "bFilter": true,
  "scrollX": true,
  "searching": false,
  "dom": '<"row"<"col-sm-6"<"pull-left"f>l><"col-sm-6 container-right text-right"B>><"row"<"col-sm-12"t>><"row"<"col-sm-5"i><"col-sm-7"p>>',
  "lengthMenu": [
    [10, 100, 1000, 5000],
    [10, 100, 1000, 5000]
  ],
  "pageLength": 10,
  ajax: {
    url: "https://microsoftedge.github.io/Demos/json-dummy-data/64KB.json",

    data: {
      customParam1: 'value1', // Example additional parameter
    },
    dataSrc: "", // Use an empty string to tell DataTables to use the root array of objects

  },
  columns: [{
      data: "name"
    }, // Maps 'name' field in JSON to first column
    {
      data: "language"
    }, // Maps 'language' field in JSON to second column

  ],
  "buttons": [

    {
      extend: 'collection',
      text: '<i class="fa fa-download m-r-xs"></i>Down Load',
      titleAttr: '',
      className: "btn-sm btn-default dropdown-menu-left",
      buttons: [{
          extend: 'excelHtml5',
          text: 'Excel',
          exportOptions: {
            columns: ':visible',
          },
          customize: function (xlsx) {
									var sheet = xlsx.xl.worksheets['sheet1.xml'];
									var styles = xlsx.xl['styles.xml'];
									var cellXfs = styles.getElementsByTagName('cellXfs')[0];

									// Create new styles for left, center, and center-right alignment
									var leftAlignStyle = '<xf xfId="0" applyAlignment="1"><alignment horizontal="left" vertical="center"/></xf>';
									//var centerAlignStyle = '<xf xfId="0" applyAlignment="1"><alignment horizontal="center" vertical="center"/></xf>';
                  
                  // Create new styles for center and bold alignment
                  var centerAlignStyle = '<xf xfId="0" applyAlignment="1" applyFont="1"><alignment horizontal="center" vertical="center"/><font><b/></font></xf>';

									var leftAlignIndex =...