NyhmMy site requires custom augmentation of the login form. The custom fields are added via the do_action('login_form') action hook.
However, sidebar-login never calls this. Any other plugins that expect to add custom login fields cannot work without directly hacking sidebar-login.php (which breaks upon update).
Please add the following one-line enhancement:
<form method="post" action="<?php echo $sidebarlogin_post_url; ?>">
...
do_action('login_form');
...