No Config Files after Purge and Reinstall

I have had a new public Ubuntu 18.04 LTS server for about three weeks. I set up the DNS and initially installed nginx and then later Jitsi. Certbot did its stuff and I could access nginx but not Jitsi via https//mydomain.org and www.mydomain.org. I could not access Jitsi and wanted to put a reverse Proxy on it so that the general public could not discover and use it.

At that point things went wrong because I did not understand nginx server blocks/virtual servers. It seemed broken, so I removed, purged and reloaded. It still would not work even as it did at the beginning. I have purged and reinstalled about 10 times, going deeper and deeper with removal of all files and related folders in /etc, /var and /usr.

I have just installed everything again. In /etc/nginx are an empty conf.d folder and the following files: ~modules, mime.types, nginx.conf and win-utf. There are no sites-available or site-enabled folders.

I am at a complete loss, because I do not understand where the configuration files come from. I have tried creating them but was never successful. After about ten days of seemingly futile effort, I think my marriage is suffering!

Does anyone have any advice please.