Allow special cheracter in email address and create username automatically

username_email_creation.php

<?php

add_action( 'wfacp_before_process_checkout_template_loader', function () {
   add_action( 'woocommerce_checkout_process', function () {
       $instance = WFACP_Core()->template_loader->get_template_ins();
       remove_filter( 'woocommerce_checkout_posted_data', [ $instance, 'assign_email_as_a_username' ] );
   } );
} );