Actually this forum works through an Apache reverse proxy with authentication and it works, so I suspect that the problem has to do with jwilder/nginx-proxy. Since we don't have this here, all I can propose is that you do debugging yourself. Run elogd with the -v flag so that you see all requests coming from the user through the proxy. Compare the requests through Apache and Nginx to see if any argumets are stripped or mangled. Upon successful login, elog sets a cookie with a unique session-ID (the cookie name is "sid") to the browser. If you proxy strips that cookie, you would land on the login page. Maybe look in that direction.
Yes, I tried setting the URL parameter to the url used by the proxy. It goes to the correct address but that landing is the login page.
Have you tried the "URL = ..." statement? This determines you elog redirects if you log in. If you reach elog through a proxy, the URL is a different one that if you access it directly. In your case the proxy URL might be necessary.
I've been trying to configured a Synology NAS to run my personal elog with a reverse proxy to the outside world. The best way seems to be running Elog in a Docker instance and then running a separate connected Docker running a nginx-proxy (in this case jwilder/nginx-proxy). This second container manages the certificates to letsencrypt and mapping URL requests to relevant containers so that connection is secured properly.
It worked great in the initial test. However, I have an issue with authentication. When I password protect the elog it goes to a login page. When I give an correct password it loops back to the login page (incidentally when I give an incorrect password it gives an 'Invalid user name or password!' warning). So I know that its getting the correct password but there is some issue that is resetting or ignoring the authentication. I am never able to actually get to the protected content.
Does anyone have any experience in using Nginx to setup a secure reverse proxy? Any insights into why this would mess with the authentication of elog?
Side note: I have tried using Apache to do the same and authentication worked fine. But the pre-canned jwilder/nginx-proxy docker manages all the certificates automatically and seamlessly and allows me to have multiple services running on the same outward facing port on my router. There is no equivalent (as far as I know) that uses Apache for proxying with letsencrypt.