Filter the PMPro Login URL for sites.

filter-pmpro-login-url.php

<?php
/**
 * Adjust the login URL value that PMPro uses and override it to use a custom one.
 * Use this to force the login URL even if the frontend URL page is set.
 * You can tweak this further based on current page, condtionals and more. This is a starting point.
 * To add this code to your site follow this guide - https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
function my_pmpro_login_url( $login_url, $redirect, $reauth ) {
  
  $login_url = '/login'; // Change the slug of this.
  
   if ( ! empty( $redirect ) ) {
        $login_url = add_query_arg( 'redirect_to', urlencode( $redirect ), $login_url );
    }
  
  return $login_url;
}
add_filter( 'pmpro_login_url', 'my_pmpro_login_url', 10, 3 );