The error log you posted does mention issues with the session. Maybe this - https://stackoverflow.com/questions/19004460/cakephp-error-unable-to-configure-the-session-setting-session-auto-start-faile
This stack overflow issue sounds similar to yours: https://stackoverflow.com/questions/62117382/shifted-cake-php-project-to-new-hoisting-getting-this-error-cake-error-excepti
Is there helpful written to the <installdir>/logs files?</installdir> My best guess it it seems like some permission issue.
What page are you trying to access? Does it do this on the main / login page? It is never a bad idea to check the permissions on the <install dir="">/tmp dir and make sure that the web user has access to write to it. That not being set can cause all sort of issues.</install>
I have never seen that one before. Give the 6.0 Release a try. It works with the hosting company I am using. They use cPanel as well and latest PHP. https://github.com/nazgul26/PHPRecipebook/releases/tag/6.0.beta This release might have a couple rough edges but better then a non working install.
MySql and Maria db are similair... but I have done most testing with MySQL and Postgres. You have the SQL that is causing the error?
What format are you looking to export? And can you move this request over to the github page. Find an existing issue on exports or open a new one with your request. https://github.com/nazgul26/PHPRecipebook/issues
The main content is in this div: <div id="main" class="constrain borderStyle"> You can use the id 'main' or add/modify the classes it uses. For example you could change constrain class to justify/margin they way you want. Be aware though that the app uses sass to create the css file, so you will want to do that to compile the css output file.