I finally scrapped that install and tried another one.
php artisan migrate step seems to be missing in the installation guide. It looks like that step is required to populate the database.
The next problem I ran into was that the
/public/setup page looked off, it was not rendering the app.js and app.css files correctly.
public/index.php/setup/js/app.js were leading to a 404. I did manage to complete the installation, but was never able to get the app.js and app.css to render correctly.
I might encourage people that work on the development of Invoice Ninja to try and install Invoice Ninja on a shared hosting account - one where you don’t have root access - and see what issues may come up so that a guide can be written better.