Change Magento 2 website based on IP

I've had the same issue, I'm using geoplugin to get the country of my customers ip address. I also have a cookie just in case the customer after being redirected to a store let's say in Portuguese actually prefers to use the English version, I store a value in the cookie so the customer doesn't get redirected back to the Portuguese version. Let me know if you need any further assistance and don't forget to upvote / mark as answer if this solved your problem :)

In your etcevents.xml

<event name="controller_action_postdispatch">
        <observer name="controller_action_postdispatch" instance="VendorModuleObserverPostDespatchEvent" />
    </event>

In your VendorModuleObserverPostDespatchEvent.php

<?php
namespace VendorModuleObserver;

use MagentoFrameworkEventObserverInterface;
use MagentoStoreModelStoreManagerInterface;
use MagentoFrameworkAppHelperAbstractHelper;
use MagentoFrameworkAppConfigScopeConfigInterface;
use MagentoFrameworkStdlibCookieCookieMetadataFactory;
use MagentoFrameworkStdlibCookieManagerInterface;
use MagentoFrameworkSessionSessionManagerInterface;

class PostDespatchEvent implements ObserverInterface
{  

    /**
     * Name of Cookie that holds private content version
     */
    CONST COOKIE_NAME = 'COOKIE_DEFAULT_LANG_CUSTOM';

    /**
     * Cookie life time
     */
    CONST COOKIE_LIFE = 3600;

    /**
     * @var MagentoFrameworkStdlibCookieManagerInterface
     */


    protected $_storeManager;
    protected $cookieManager;
    protected $cookieMetadataFactory;
    private   $scopeConfigInterface;

    protected $checkoutSession;
    protected $cart;
    protected $customerSession;
    
    public function __construct(
        StoreManagerInterface                           $storeManager,
        ScopeConfigInterface                            $scopeConfigInterface,
        CookieManagerInterface                          $cookieManager,
        CookieMetadataFactory                           $cookieMetadataFactory,
        SessionManagerInterface                         $sessionManager,
        MagentoCheckoutModelSession                 $checkoutSession,
        MagentoCheckoutModelCart                    $cart,
        MagentoCustomerModelSession                 $customerSession
        
    ) {
        $this->_storeManager = $storeManager;
        $this->scopeConfigInterface = $scopeConfigInterface;
        $this->cookieManager = $cookieManager;
        $this->cookieMetadataFactory = $cookieMetadataFactory;
        $this->sessionManager = $sessionManager;

        $this->checkoutSession = $checkoutSession;
        $this->cart            = $cart;
        $this->customerSession = $customerSession;
    }

    public function getCookie($name)
    {
        return $this->cookieManager->getCookie($name);
    }
    public function setCookie($value, $duration = 604800)
    {
        $metadata = $this->cookieMetadataFactory
            ->createPublicCookieMetadata()
            ->setDuration($duration)
            ->setPath($this->sessionManager->getCookiePath())
            ->setDomain($this->sessionManager->getCookieDomain());

        $this->cookieManager->setPublicCookie(self::COOKIE_NAME, $value, $metadata);

    }

    public function execute(MagentoFrameworkEventObserver $observer)
    {

        $cookie = self::getCookie(SELF::COOKIE_NAME);
        if(!isset( $cookie))
        {
            $countryCode = SELF::ip_info("Visitor", "Country Code"); 

            if($countryCode == 'PT')
            {            
                $this->_storeManager->setCurrentStore('default');                
            }
            else
            {
                if($countryCode == 'DE')
                {            
                    $this->_storeManager->setCurrentStore('DE');
                }
                else
                {
                    $this->_storeManager->setCurrentStore('EN');
                }
           }

             self::setCookie( SELF::COOKIE_NAME);
        }
    }

    public static function ip_info($ip = NULL, $purpose = "location", $deep_detect = TRUE) {
        $output = NULL;
        if (filter_var($ip, FILTER_VALIDATE_IP) === FALSE) {
            $ip = $_SERVER["REMOTE_ADDR"];
            if ($deep_detect) {
                if (filter_var(@$_SERVER['HTTP_X_FORWARDED_FOR'], FILTER_VALIDATE_IP))
                    $ip = $_SERVER['HTTP_X_FORWARDED_FOR'];
                if (filter_var(@$_SERVER['HTTP_CLIENT_IP'], FILTER_VALIDATE_IP))
                    $ip = $_SERVER['HTTP_CLIENT_IP'];
            }
        }
        $purpose    = str_replace(array("name", "n", "t", " ", "-", "_"), NULL, strtolower(trim($purpose)));
        $support    = array("country", "countrycode", "state", "region", "city", "location", "address");
        $continents = array(
            "AF" => "Africa",
            "AN" => "Antarctica",
            "AS" => "Asia",
            "EU" => "Europe",
            "OC" => "Australia (Oceania)",
            "NA" => "North America",
            "SA" => "South America"
        );
        if (filter_var($ip, FILTER_VALIDATE_IP) && in_array($purpose, $support)) {
            $ipdat = @json_decode(file_get_contents("http://www.geoplugin.net/json.gp"));
            if (@strlen(trim($ipdat->geoplugin_countryCode)) == 2) {
                switch ($purpose) {
                    case "location":
                        $output = array(
                            "city"           => @$ipdat->geoplugin_city,
                            "state"          => @$ipdat->geoplugin_regionName,
                            "country"        => @$ipdat->geoplugin_countryName,
                            "country_code"   => @$ipdat->geoplugin_countryCode,
                            "continent"      => @$continents[strtoupper($ipdat->geoplugin_continentCode)],
                            "continent_code" => @$ipdat->geoplugin_continentCode
                        );
                        break;
                    case "address":
                        $address = array($ipdat->geoplugin_countryName);
                        if (@strlen($ipdat->geoplugin_regionName) >= 1)
                            $address[] = $ipdat->geoplugin_regionName;
                        if (@strlen($ipdat->geoplugin_city) >= 1)
                            $address[] = $ipdat->geoplugin_city;
                        $output = implode(", ", array_reverse($address));
                        break;
                    case "city":
                        $output = @$ipdat->geoplugin_city;
                        break;
                    case "state":
                        $output = @$ipdat->geoplugin_regionName;
                        break;
                    case "region":
                        $output = @$ipdat->geoplugin_regionName;
                        break;
                    case "country":
                        $output = @$ipdat->geoplugin_countryName;
                        break;
                    case "countrycode":
                        $output = @$ipdat->geoplugin_countryCode;
                        break;
                }
            }
        }
        return $output;
    }
}


?>