Does anybody know if there have been changes to the way XML files from custom themes are included in Version 2.3? I have a very simple XML file to modify the Magento Advanced Search page. The custom .phtml file works fine from my version 2.2 mod, but the XML file doesn't seem to work since the upgrade.
<?xml version="1.0"?>
<!--
/**
* Copyright © Magento, Inc. All rights reserved.
* See COPYING.txt for license details.
*/
-->
<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" layout="1column" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
<head>
<css src="css/AdvancedSearch.css" media="all and (min-width: 1px)" />
</head>
<body>
<referenceBlock name="page.main.title" display="false" />
</body>
</page>
The above is the custom XML file that worked fine in 2.2 but does not seem to work in 2.3. All it does is removes the pages title and includes a custom CSS file
EDIT---------------------------------------- I copied the above code into the core XML file at /vendor/magento/module-catalog-search/view/frontend/layout and it is working as expected. However it doesnt work from the custom theme, even though the .phtml is fine and it worked in 2.2. Is there a reason why custom theme XML files might not be included?
<referenceBlock name="category_list_on_left" remove="true"/>
?