Show Custom Post Types in Gravity Form Select Field

functions.php

<?php
/* Show Custom Post Types in Gravity Form Select Field */
add_filter( 'gform_pre_render_2', 'populate_cpt_titles' );
add_filter( 'gform_pre_validation_2', 'populate_cpt_titles' );
add_filter( 'gform_pre_submission_filter_2', 'populate_cpt_titles' );
add_filter( 'gform_admin_pre_render_2', 'populate_cpt_titles' );
function populate_cpt_titles( $form ) {
	foreach ( $form['fields'] as &$field ) {
		if ( $field->type != 'select' || strpos( $field->cssClass, 'populate_cpt_titles' ) === false ) {
	    		continue;
		}

		$field->placeholder = 'Select Service';

		$args = [
			'posts_per_page'   => -1,
			'order'            => 'ASC',
			'orderby'          => 'post_title',
			'post_type'        => 'service', // Change this to your Custom Post Type
			'post_status'      => 'publish',
		];
		$custom_posts = get_posts( $args );

		$options = [];
		foreach( $custom_posts as $custom_post ) {
			$options[] = ['text' => $custom_post->post_title, 'value' => $custom_post->post_title];
		}

		$field->choices = $options;
	}

	return $form;
}