Alternate events tickets template part that will display an external link to register instead of a ticket selector. This can be uploaded to your child theme along with the other templates from the espresso Arabica child theme. http://eventespresso.com/topic/alternate-registration-page-not-woking-ee4/

content-espresso_events-tickets.php

<?php global $post; ?>
<br/>
<div class="event-tickets">
	<h3 class="ticket-selector-h3 ee-event-h3">
		<span class="ee-icon ee-icon-tickets"></span><?php _e( 'Ticket Options', 'event_espresso' ); ?>
	</h3>
	<?php
	$alt_url = '<a class="button" href="' . $post->EE_Event->external_url() . '">Click through to register for this event</a>';
	if ( $post->EE_Event->external_url() !== NULL && $post->EE_Event->external_url() !== '' ) {
		echo $alt_url;
	} else { 
		espresso_ticket_selector( $post );
	} ?>
</div>
<!-- .event-tickets -->