Question: I use [Locale](https://docs.oracle.com/javase/8/docs/api/java/util/Locale.html) and have displayed language in `String`, for example "English". Is it possible to convert it to language tag(`en`)?

Answer: 
It's in [\Magento\Sales\Model\ResourceModel\Order\Handler\State](https://github.com/magento/magento2/blob/2.4-develop/app/code/Magento/Sales/Model/ResourceModel/Order/Handler/State.php) which is called whenever the Order is saved.
In "Magento\Sales\Model\ResourceModel\Order" there is a function Save(). Within the function you can retrieve and modify value of 'status' of Order.
Writing a plugin is preferable.

di.xml

```
<type name="Magento\Sales\Model\ResourceModel\Order">
    <plugin name="after_plugin_order_state" type="Vendor\Module\Plugin\PluginName"/>
</type>

```

PluginName.php

```
public function afterSave(
    \Magento\Sales\Model\ResourceModel\Order $subject,
     $result,$object
){
    $setCustomStatus = $object->setData('status','Complete');
    return $result
 }

```