How to add custom view to django admin interface?

You have 3 options here:

Using third-party packages which provide menu

This is pretty straight forward, there are some good packages out there which support menu for admin, and some way to add your item to the menu.

An example of a 3rd party package would be django-admin-tools. The drawback is that it is a bit hard to learn. Another option would be to use django-adminplus but at the time of writing this, it does not support Django 2.2.

Hacking with django admin templates

You can always extend admin templates and override the parts you want, as mentioned in @Sardorbek answer, you can copy some parts from admin template and change them the way you want.

Using custom admin site

If your views are supposed to only action on admin site, then you can extend adminsite (and maybe change the default), beside from adding links to template, you should use this method to define your admin-only views as it's easier to check for permissions this way.

Considering you already extended adminsite, now you can use the previous methods to add your link to template, or even extend get_app_list method, example:

class MyAdminSite(admin.AdminSite):
    def get_app_list(self, request):
        app_list = super().get_app_list(request)
        app_list += [
            {
                "name": "My Custom App",
                "app_label": "my_test_app",
                # "app_url": "/admin/test_view",
                "models": [
                    {
                        "name": "tcptraceroute",
                        "object_name": "tcptraceroute",
                        "admin_url": "/admin/test_view",
                        "view_only": True,
                    }
                ],
            }
        ]
        return app_list

You can also check if current staff user can access to module before you show them the links. It will look like this at then end:

Problem here that your div is not inside main-content. I suggest extending admin/index.html

Put in app/templates/admin/index.html

{% extends "admin/index.html" %}
{% load i18n static %}

{% block content %}
<div id="content-main">

{% if app_list %}
    {% for app in app_list %}
        <div class="app-{{ app.app_label }} module">
        <table>
        <caption>
            <a href="{{ app.app_url }}" class="section" title="{% blocktrans with name=app.name %}Models in the {{ name }} application{% endblocktrans %}">{{ app.name }}</a>
        </caption>
        {% for model in app.models %}
            <tr class="model-{{ model.object_name|lower }}">
            {% if model.admin_url %}
                <th scope="row"><a href="{{ model.admin_url }}">{{ model.name }}</a></th>
            {% else %}
                <th scope="row">{{ model.name }}</th>
            {% endif %}

            {% if model.add_url %}
                <td><a href="{{ model.add_url }}" class="addlink">{% trans 'Add' %}</a></td>
            {% else %}
                <td>&nbsp;</td>
            {% endif %}

            {% if model.admin_url %}
                {% if model.view_only %}
                <td><a href="{{ model.admin_url }}" class="viewlink">{% trans 'View' %}</a></td>
                {% else %}
                <td><a href="{{ model.admin_url }}" class="changelink">{% trans 'Change' %}</a></td>
                {% endif %}
            {% else %}
                <td>&nbsp;</td>
            {% endif %}
            </tr>
        {% endfor %}
        </table>
        </div>
    {% endfor %}

    <!-- here you could put your div -->
    <div class="app-sonstiges module">
    ....
    </div>
    <!-- here you could put your div -->
{% else %}
    <p>{% trans "You don't have permission to view or edit anything." %}</p>
{% endif %}
</div>
{% endblock %}

The another approach is to add custom app to app_list. But it is far more ugly. So I suggest overriding template.

I assume you are overriding get_urls in AdminSite.