Magento2 Backend Locale – How to Change the Locale of Admin Backend

Whenever you add a configuration section for a module using a system.xml you need the corresponding ACL.

Example if you have a system.xml that looks like this:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Config:etc/system_file.xsd">
    <system>
        <tab id="vendor" translate="label" sortOrder="300">
            <label>Vendor</label>
        </tab>
        <section id="module" translate="label" type="text" sortOrder="140" showInDefault="1" showInWebsite="1" showInStore="1">
            <tab>vendor</tab>
            ...
        </section>
    </system>
</config>

Then you will need an etc/acl.xml file that looks like this:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Acl/etc/acl.xsd">
    <acl>
        <resources>
<resource id="Magento_Backend::system">
                    <resource id="Vendor_Module::vendor" title="Vendor" sortOrder="100">
                        <resource id="Vendor_Module::module" title="Module" sortOrder="100"/>
                    </resource>
                </resource>
            </resource>
        </resources>
    </acl>
</config>