I have created a child theme of parent theme, and declared default_head_blocks.xml at
<child_theme_dir>/Magento_Theme/layout folder with following content:
<?xml version="1.0"?>
<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../vendor/magento/framework/Module/etc/module.xsd">
<head>
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1.0, user-scalable=no"/>
<css src="css/custom.css" media="all"/>
<css src="css/custom_responsive.css" media="all"/>
</head>
</page>
and created these 2 css files in directory:
<child_theme_dir>/web/css
and put my custom styles in those files, deleted all static content form pub folder, deployed static content, cleared all caches but still when I check on front end, the custom.css is not included in output, not sure what I am doing wrong while this seems to be standard process as given here ( https://devdocs.magento.com/guides/v2.4/frontend-dev-guide/css-topics/css-themes.html ) and I did it many times before too.
TIA
---- Added theme.xml & registration.php ---
Though personally I think they have no relation with my problem, still sharing the same, I have personally verified by making changes in other files in my child theme and the changes are getting applied
<!--
/**
* Copyright © 2015 Magento. All rights reserved.
* See COPYING.txt for license details.
*/
-->
<theme xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Config/etc/theme.xsd">
<title>Egon gemsone</title>
<parent>Mgs/claue</parent>
<media>
<preview_image>media/preview.jpg</preview_image>
</media>
</theme>
registration.php file
<?php
/**
* Copyright © 2015 Magento. All rights reserved.
* See COPYING.txt for license details.
*/
\Magento\Framework\Component\ComponentRegistrar::register(
\Magento\Framework\Component\ComponentRegistrar::THEME,
'frontend/Egon/gemsone',
__DIR__
);