Dynamic Advanced Custom Fields public custom post type select field.

acf_cpt_dynamic_select.php

<?php
/*
* Add this snippet to your functions.php file
* Create a select field through ACF (can be used in flexible content, repeater, etc.)
* Leave the choices field blank in the ACF backend
* Add it to your page.
*/
function acf_load_cpt_field_choices( $field ) {

     // Reset choices
     $field['choices'] = array();
     
     //Get only public custom post typoes 
     $args = array(
           'public'   => true,
           '_builtin' => false
        );

        $output = 'names'; // names or objects, note names is the default
        $operator = 'and'; // 'and' or 'or'

        $choices = get_post_types( $args, $output, $operator );

     // loop through array and add to field 'choices'
     if( is_array($choices) ) {

         foreach( $choices as $choice ) {

             $field['choices'][ $choice ] = $choice;

         }

     }

     // return the field
     return $field;

 }
//Ensure the name is the name of the select field you want populated.
add_filter('acf/load_field/name=cpt_select', 'acf_load_cpt_field_choices');