The WP Favicon Remover plugin adds the functionality to remove the WordPress default favicon since WordPress 5.4. If the favicon does not change after the plugin install, you have to clear the browser cache. If you use Site Icon via Theme Customizer, just uninstall this plugin.
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WP Favicon Remover
安装:
Copy the wp-favicon-remover directory into your wp-content/plugins directory
Activate the plugin through the 'Plugins' menu in WordPress