Uncanny Import Users: Automatically give the user the default role when the user exists in the network, but not on the site.

main.php

<?php

class Sample {
  public function __construct() {
		$this->hooks();
	}
  
  public function hooks() {
    add_action( 'uo_after_user_row_imported', array( $this, 'add_user_to_multisite' ), 99, 4 );
  }
  
  public function add_user_to_multisite( $user_id, $current_row, $csv_header, $key_location ) {
		$user = new \WP_User( $user_id );
		if ( empty( $user->roles ) ) {
			$user->add_role( get_option( 'default_role' ) );
		}
	}
  
}

new Class();