Event::on(
    Cp::class,
    Cp::EVENT_REGISTER_CP_NAV_ITEMS,
    function(RegisterCpNavItemsEvent $event){
        // the 4th element is the "User", you can change the URL to your
        // custom controller instead of the default template
        // I suggest you to loop all `navItems` and find
        // the correct user instead of assuming it's the 4th
        // Craft::dd($event->navItems);
        $event->navItems[4]['url'] = ['template' => 'path/to/template/user'],
});

{% if CraftEdition != CraftPro %}
    {% exit 404 %}
{% endif %}

{% requirePermission 'editUsers' %}

{% extends "_layouts/elementindex" %}
{% set title = "Users"|t('app') %}
// changes start
// replace the elementType with your custom element type
{% set elementType = 'prefix\namespace\elements\User' %}
// changes end
{% block actionButton %}
    {% if currentUser.can('registerUsers') %}
        <a class="btn submit add icon" href="{{ url('users/new') }}">{{ "New user"|t('app') }}</a>
    {% endif %}
{% endblock %}

class User extends craftelementsUser{ //<-- extend the default User element

    /**
     * @inheritdoc
     */
    protected static function defineSources(string $context = null): array
    {
        $sources = [
            [
                'key' => '*',
                'label' => Craft::t('app', 'All users'),
                'criteria' => ['status' => null],
                'hasThumbs' => true
            ]
        ];

        // Overwrite the sources / usergroups...
        // usually Craft will search for usergroups at this place..
        // just leave it empty, so you'll only see the "default" group

        return $sources;
    }
}