Add custom class to Genesis .entry-header

functions.php

add_filter('genesis_attr_entry-header', 'lunarwp_attributes_entry_header');
/**
 * Add attributes for header entry-header element.
 *
 * @since 1.0.0
 *
 * @param array $attributes Existing attributes.
 * @return array Amended attributes.
 */
function lunarwp_attributes_entry_header($attributes)
{
	if (is_page() && ! is_home() && ! is_front_page())
	{
		$attributes['class'] .= ' lunarwp-entry-header';
	}

	return $attributes;
}