Use Bootstrap 5 as Layout base

html/mod_menu/collapse-default.php

@@ -0,0 +1,40 @@
+<?php
+/**
+ * @package     Joomla.Site
+ * @subpackage  mod_menu
+ *
+ * @copyright   (C) 2021 Open Source Matters, Inc. <https://www.joomla.org>
+ * @license     GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+defined('_JEXEC') or die;
+
+use Joomla\CMS\Helper\ModuleHelper;
+use Joomla\CMS\HTML\HTMLHelper;
+use Joomla\CMS\Language\Text;
+
+
+$id = '';
+if ($tagId = $params->get('tag_id', ''))
+{
+    $id = ' id="' . $tagId . '"';
+}
+
+?><nav class="navbar navbar-expand-lg">
+    <div class="container-fluid">
+        <button class="navbar-toggler navbar-toggler-right" type="button" data-bs-toggle="collapse" data-bs-target="#navbar<?php echo $module->id; ?>" aria-controls="navbar<?php echo $module->id; ?>" aria-expanded="false" aria-label="<?php echo Text::_('MOD_MENU_TOGGLE'); ?>">
+            <span class="icon-menu" aria-hidden="true"></span>
+        </button>
+        <div class="collapse navbar-collapse" id="navbar<?php echo $module->id; ?>">
+            <ul<?php echo $id; ?> class="navbar-nav me-auto <?php echo $class_sfx; ?>">
+                <?php foreach ($list as $i => &$item)
+                {
+                    if (count($item->tree) == 1) {
+                        require ModuleHelper::getLayoutPath('mod_menu', 'item');
+                    }
+                }
+                ?>
+            </ul>
+        </div>
+    </div>
+</nav>