Hook um_{$key}_form_show_field

um_key_form_show_field.php

<?php

/**
 * Hook: um_{$key}_form_show_field
 *
 * Type: filter
 *
 * Description: Change field HTML by field $key.
 *
 * @example https://github.com/ultimatemember/ultimatemember/blob/master/includes/core/class-fields.php#L4468
 * @link    https://docs.ultimatemember.com/article/1322-umkeyformshowfield
 *
 * @package um\core
 * @see     um\core\Fields::view_field()
 * @since   2.0
 * @version 3.0
 *
 * @param string $output Field HTML.
 * @param string $mode   Form mode.
 *
 * @return string Field HTML.
 */
function my_key_form_show_field( $output, $mode ) {
	if ( 'login' === $mode ) {
		// your code here.
	}
	return $output;
}
$key = 'user_email';
add_filter( "um_{$key}_form_show_field", 'my_key_form_show_field', 10, 2 );