How To Load Child Themes Style Sheet in Block Themes

Use this PHP code in your child themes functions file.

add_action( 'wp_enqueue_scripts', 'child_enqueue_parent_styles' );
function child_enqueue_parent_styles() {

    wp_enqueue_style( 'parent-style', get_template_directory_uri() . '/style.css' );
    
    wp_enqueue_style('child-style', get_stylesheet_directory_uri() . '/style.css', array('parent-style') );

}

You can then add custom CSS rules to your child themes style.css file when using block themes like Twenty Twenty Four etc.