This is what I have done from my end. Initially, it was with IP address so I just followed the procedure given in your docs.
First I changed /opt/bitnami/apps/ghost/htdocs/config.production.json. Below is what is there inside the json.
Followed by bnconfig with
sudo /opt/bitnami/apps/ghost/bnconfig --machine_hostname blog.abcdef.com
Also, did a mistake of changing /opt/bitnami/apps/ghost/config.js but I reverted. Post making all the changes, I have restarted the service.
Currently, /opt/bitnami/apps/ghost/htdocs/config.js is blank and there is nothing.
There is also an error saying Ghost could not be stopped when I perform restart operation. I am not sure if this could also be helpful.
Thanks for your help.