Problem solved. For this topic to be any usefull at all:
Run into first problem trying to point and click install 2 nodebb instances( test and the actual) on the same server and obviously, both couldn't listen on the same 4567 port.
Second, did the second install from the old docs on readthedocs instead of the official ones from nodebb.
Third, forgot to also add php-fpm directives to my Nginx config. And start Mongodb.