How to change Opencart template if user logged in from mobile phone?

Question

opencart

Hello. How to change Opencart template if user logged in from mobile phone?
In the /system/startup.php file, I included the mobile detect library.

// Библиотека определения мобильных устройств
require_once(DIR_SYSTEM . 'library/Mobile_Detect.php');
$detect = new Mobile_Detect(); 
define('isMobile', $detect->isMobile(), false);
define('isTablet', $detect->isTablet(), false);

Now I want to check and change the template, but I don’t know where to put it.

//Mobile
if(isMobile && !isTablet && $_COOKIE['ver'] !== 'full'){
     $this->config->set('config_template', 'default_mobile');
}elseif(isMobile && !isTablet && $_COOKIE['ver'] == 'full'){
     $this->config->set('config_template', 'default');
}

At what point and where does Opencart check which template is set by default?? OC version 2.3.x