Completely disable RSS feeds on WP 5.5.2 and show a 404 page instead of die();

You need to define the HTTP Response code in wp_die function.

wp_die( __('No feed available,please visit our <a href="'. get_bloginfo('url') .'">homepage</a>!'), '', 404 );

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)