Set default quantity of 1 and READONLY for all tickets: Same as https://gist.github.com/cliffordp/5b57df71be8b52f595817ddbf81acdab except make quantity readonly

functions.php

<?php
/**
  * Set default quantity of 1 and READONLY for all tickets:
  * - Event Tickets RSVP
  * - Event Tickets Plus WooCommerce
  * - Event Tickets Plus Easy Digital Downloads
  *
  * From https://gist.github.com/cliffordp/80b33455779b74ec49f6ea3033cb47bf
  *
  * Same as https://gist.github.com/cliffordp/5b57df71be8b52f595817ddbf81acdab except make quantity readonly
  * Watch out if you have more than 1 ticket per event!
  *
  * ! You may want to use https://gist.github.com/cliffordp/9a457b724e38b3036f8d48adc90930ed instead!
  */
function cliff_all_tickets_default_quantity_and_readonly() {
	// bail if not on a Single Event page
	if ( ! function_exists( 'tribe_is_event' ) || ! tribe_is_event() ) {
		return false;
	}
	
	wp_enqueue_script( 'jquery' );
	?>
	<script type="text/javascript">
		jQuery(document).ready( function () {
			// RSVP, Woo, and EDD tickets default to quantity of 1
			jQuery( 'input.tribe-ticket-quantity, .woocommerce .quantity input.qty, .edd.quantity input.edd-input' ).val( 1 ).attr( 'readonly', true );
			
			// CSS to display RSVP tickets' "Send RSVP confirmation to" fields
			// Note: will continue to show even if user changes quantity to zero because we didn't bind to the field to continually watch it
			jQuery( 'tr.tribe-tickets-meta-row' ).show();
		});
	</script>
	<?php
}
add_action( 'wp_footer', 'cliff_all_tickets_default_quantity_and_readonly' );

input.tribe-ticket-quantity should be input.tribe-tickets-quantity. not sure if this was a change in the class name on the field, or a typo