In the terminal output you pasted in a comment above I see you were using the config-load command, if not properly used it could easily break your server.
If you choose WP when created a site you will have WordPress installed when you go to the browser, it's a clean install and you need to start the configuration process, we don't create undesired users as EE does.
On the other hand, do you think it's an issue with 18.04?