In Magento 2.* we could extend core layouts using custom theme, for instance, (assuming our custom theme is named Custom/our_theme) if we want to remove header & footer in customer login page we did
app/design/frontend/Custom/our_theme/Magento_Customer/layout/customer_account_login.xml
<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" layout="1column" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
<body>
<referenceContainer name="footer" remove="true"/>
<referenceContainer name="header.container" remove="true"/>
</body>
</page>
However, in Magento 2.3 that way to extend layouts seem to have no effect. The strange thing is we can load CSS changes, override templates, etc... with no problem, so it is clear custom theme is well registered & it is working
But the only way to change layout structure seem to be doing it in a custom module (using layout_load_before event, for instance)
Is this a common issue? I mean, have you faced this in Magento 2.3 here? Or should we assume there is something wrong in our project?
UPDATE
We've seen that applying changes as layout updates then it does work
<layout xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_layout.xsd">
<referenceContainer name="footer" remove="true" />
<referenceContainer name="header.container" remove="true" />
</layout>
What I don't understand is why the first way (including page & body tags) has stopped working
<?xml version="1.0"?>
see my answer its working fine.