Why do you have to use NGINX? Caddy does the proxying to the Lemmy containers for you. That docker-compose.yml file is my entire deployment, there is no hidden NGINX container or config file that needs to be added. Just remove your broken Lemmy deployment with docker compose down and delete the containers, then docker compose up my docker-compose.yml (after you edit the postgres variables) with config.hjson in the same folder.

Oh shit, I forgot that your Caddy would be running on a bridge network by default because mine is on the host network where all ports are already exposed to it! (It’s generally a bad idea to use the host network, so don’t do this if you’re only using Caddy with containers on the same network) I edited the Gist to expose 80 and 443 for HTTP/S on that container, the updated file uses the same Github link. Really sorry about that!

Ugh, that one is a problem with indentation because pasting the config into a Lemmy comment destroys the formatting. I uploaded it on Github to preserve the correct indentation.

Yeah, the config file on the documentation sucks. I had to poke through several discussions on /c/selfhosting to find a config that wasn’t the extremely minimal one linked in the documentation. Your config.hjson is fine from what I can tell, although I’m not sure why you censored the hostname there as it’s supposed to be lemmy.emphisia.nl and not anything confidential.

Honestly, I don’t have enough understanding of NGINX to debug its config, so I’ll just share my docker-compose.yml for leddit.danmark.party which worked correctly and federated out of the box, with a few adjustments to match your deployment. Note that you’ll have to tear down your existing deployment if you want to use this docker-compose.yml because they use the same ports.

version: "3.9"
x-logging:
  &default-logging
  options:
    max-size: '10m'
  driver: json-file

services:
  caddy:
    image: caddy:2
    volumes:
      - ./volumes/caddy:/data
      - ./volumes/caddy:/config
    # See Caddy's documentation for customizing this line
    # https://caddyserver.com/docs/quick-starts/reverse-proxy
    command:
      - /bin/sh
      - -c
      - |
        cat <<EOF > /etc/caddy/Caddyfile && caddy run --config /etc/caddy/Caddyfile
        
        {
          debug
        }
        
        (common) {
        	encode gzip
        	header {
        		-Server
        		Strict-Transport-Security "max-age=31536000; include-subdomains;"
        		X-XSS-Protection "1; mode=block"
        		X-Frame-Options "DENY"
        		X-Content-Type-Options nosniff
        		Referrer-Policy no-referrer-when-downgrade
        		X-Robots-Tag "none"
        	}
        }       
        
        # Lemmy instance
        lemmy.emphisia.nl {
          log
          import common
          reverse_proxy http://lemmy-ui:1234 # lemmy-ui
          
          @lemmy {
        		path /api/*
        		path /pictrs/*
        		path /feeds/*
        		path /nodeinfo/*
        		path /.well-known/*
        	}
         
         	@lemmy-hdr {
        		header Accept application/*
        	}
          
          handle @lemmy {
            reverse_proxy http://lemmy:8085 # lemmy
          }
          
          handle @lemmy-hdr {
            reverse_proxy http://lemmy:8085
          }
          
          @lemmy-post {
        		method POST
        	}
        
        	handle @lemmy-post {
        		reverse_proxy http://lemmy:8085
        	}
        }
        EOF
    lemmy:
      image: dessalines/lemmy:0.18.1-rc.9
      ports:
        - 8085:8536
      volumes:
        - ./lemmy.hjson:/config/config.hjson
      depends_on:
        - postgres
        - pictrs
      restart: always
      logging: *default-logging
      
    lemmy-ui:
      image: dessalines/lemmy-ui:0.18.1-rc.9
      ports:
       - 1234:1234
      environment:
        - LEMMY_UI_LEMMY_INTERNAL_HOST=lemmy:8085
        - LEMMY_UI_LEMMY_EXTERNAL_HOST=localhost:1236
      depends_on:
        - lemmy
      volumes:
        - ./volumes/lemmy-ui/extra_themes:/app/extra_themes
      restart: always
      logging: *default-logging
   
    postgres:
      image: postgres:15-alpine
      ports:
        - 5432:5432
      environment:
        - POSTGRES_USER=MyPostgresUser
        - POSTGRES_DB=MyPostgresDb
        - POSTGRES_PASSWORD=MyPostgresPassword
      volumes:
        - ./volumes/postgres:/var/lib/postgresql/data
      restart: always
      logging: *default-logging
      
    pictrs:
      image: asonix/pictrs:0.4.0-rc.7
      user: 991:991
      hostname: pictrs
      environment:
        - PICTRS__MEDIA__VIDEO_CODEC=vp9
        - PICTRS__MEDIA__GIF__MAX_WIDTH=256
        - PICTRS__MEDIA__GIF__MAX_HEIGHT=256
        - PICTRS__MEDIA__GIF__MAX_AREA=65536
        - PICTRS__MEDIA__GIF__MAX_FRAME_COUNT=400
      volumes:
        - ./volumes/pictrs:/mnt
      restart: always
      logging: *default-logging
	  
    postfix:
      image: mwader/postfix-relay
      environment:
       - POSTFIX_myhostname=lemmy.emphisia.nl
      restart: "always"
      logging: *default-logging

I don’t use NGINX as my proxy server, but it’s a bit strange that you would need two configs for this while mine runs perfectly with one config and two open ports (:8536 for Lemmy-BE and :1234 for Lemmy-UI). And why are you using different versions of Lemmy-BE (18.1-rc9) and Lemmy-UI (18.1-rc4)?

If you are using the default docker-compose.yml on the Lemmy repo, that part of the NGINX config uses https:// + the name of the Docker containers. And you always give NGINX the external port (the number on the right side of the colon defined in ports:, like 1234 in 1234:5678). The port on the left is only known to the container the port is defined for.

If it’s still broken after you correct the NGINX config, what are your docker-compose.yml and config.hjson like? There’s several versions of them floating around and you might have combined incompatible versions with each other.

On 0.18.0, there is only the “Only moderators can post” checkbox which stops regular users from creating new posts, but it doesn’t stop them from commenting on posts. I’m looking for a way to prevent both (instead of deleting comments after they have been posted).

That, and for Lemmy specifically, its history of being a tankie forum. Without the Reddit refugee migration, if you joined Lemmy as a single user, you would be alone among communists and eventually get bullied into leaving. Already in 2020-2021, Fediverse users knew about Lemmy, but they avoided promoting it because of its userbase. This Reddit situation provided the push to get many normal users over to Lemmy at once to drown out the communist users.

A lot of VPS providers block port 25 (and other email ports) because they don’t want people to set up bot spam mail servers on their services. Could that be the issue?