Filter the PMPro Member Directory results by user meta value. This can be used to only display members that completed a user field with a specific value.

pmpro-directory-filter-by-user-meta.php

<?php
/**
 * Filter PMPro Member Directory by custom user meta field.
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
function my_pmpro_directory_filter_based_on_user_meta( $sql_parts, $levels, $s, $pn, $limit, $start, $end, $order_by, $order ) {
	global $wpdb;

	$meta_key   = 'meta_key'; // Change 'meta_key' to the name of your user field.
	$meta_value = 'meta_value'; // Change 'meta_value' to the value of your user field.

	$sql_parts['JOIN'] .= " LEFT JOIN $wpdb->usermeta um_field_1 ON um_field_1.meta_key = '" . esc_sql( $meta_key ) . "' AND um_field_1.user_id = u.ID ";
	$sql_parts['WHERE'] .= " AND um_field_1.meta_value = '" . esc_sql( $meta_value ) . "' ";

	return $sql_parts;
}
add_filter( 'pmpro_member_directory_sql_parts', 'my_pmpro_directory_filter_based_on_user_meta', 10, 9 );