Enable logging for Fortress by Snicco. This has not been tested on any hosting environment other than GridPane.

fortress-logging.php

<?php
/**
 * Plugin Name: Fortress Logging - Only activate when actively troubleshooting
 * Description: Enables a logging of the response event (other actions need to be made in order to have this work since fortress does not expose the response by default. 
 * Version: 0.0.1
 */

use Snicco\Bundle\HttpRouting\Event\ResponseSent;

add_action(ResponseSent::class, function (ResponseSent $event) {

    // ONLY LOG TOTP CHALLENGE.
    if (!str_contains($_SERVER['REQUEST_URI'], 'snicco-fortress/auth/totp/challenge')) {
        return;
    }
    
    // CHANGE SITE_URL to match your domain.
    $site_url = parse_url( get_site_url(), PHP_URL_HOST ) );
    
    $dir = "/var/www/$site_url/fortress/var/response_debug";
    
    if (!is_dir($dir)) {
        mkdir($dir, 0777, true);
    }
    
    // Getting the current date and time in the format YYYY-MM-DD_HH-MM-SS
    $timestamp = date('Y-m-d_H-i-s');
    
    // GET THE RESPONSE HTML AS STRING AND LOG IT.
    $response = $event->response;
    $body = $response->getBody();
    $body->rewind();
    $body_string = $body->__toString();
    
    file_put_contents("$dir/$timestamp.body.html", $body_string, LOCK_EX);
    
    // LOG THE RESPONSE HEADERS
    $headers = $response->getHeaders();
    file_put_contents("$dir/$timestamp.headers.json", json_encode($headers), LOCK_EX);
});