原因分析：

dde-grand-search/src/grand-search/utils/utils.cpp

bool Utils::launchAppByGio(const QString &desktopFile, const QStringList &filePaths)
{
    // 使用gio接口启动应用
    std::string stdDesktopFilePath = desktopFile.toStdString();
    const char *cDesktopPath = stdDesktopFilePath.data();

    GDesktopAppInfo *appInfo = g_desktop_app_info_new_from_filename(cDesktopPath);
    if (!appInfo) {
        //qDebug() << "Failed to open desktop file with gio: g_desktop_app_info_new_from_filename returns NULL. Check PATH maybe?";
        return false;
    }

    GList *g_files = nullptr;
    foreach (const QString &filePath, filePaths) {
        std::string stdFilePath = filePath.toStdString();
        const char *cFilePath = stdFilePath.data();
        GFile *f = g_file_new_for_uri(cFilePath);
        g_files = g_list_append(g_files, f);
    }

    GError *gError = nullptr;
    gboolean ok = g_app_info_launch(reinterpret_cast(appInfo), g_files, nullptr, &gError);

    if (gError) {
        qWarning() << "Error when trying to open desktop file with gio:" << gError->message;
        g_error_free(gError);
    }

    if (!ok) {
        qWarning() << "Failed to open desktop file with gio: g_app_info_launch returns false";
    }
    g_object_unref(appInfo);
    g_list_free(g_files);

    // 问题出在这里，上边已经使用 g_app_info_launch 启动过一次浏览器了，这里又通过 gio 启动了一次，
    // 所以可以注释掉下边的代码或者复制到上边的 if (!ok) {} 中
    /*
    for (auto filePath : filePaths) {
        if (!filePath.isEmpty())
            QProcess::startDetached("gio", QStringList() << "open" << filePath);
    }
    */

    return ok;
}

附编译后文件

dde-grand-search_5.4.5+kt286_amd64.zip