I finally made it work, and thought to put everything together in case someone needs it.
This info is assembled from different topics on this forum. Thanks to @brahn and @techAPJ.
This assumes you’ve completed the initial Let’s Encrypt setup:
After you’ve done it, the following needs to be added to the app.yml in hooks section. It will do two things:
- setup SSL for both example.comandwww.example.com. Just replaceexample.comwith your domain name.
- redirect example.comtowww.example.com
If anybody knows how to improve it, please let me know.
hooks:
  after_code:
    - exec:
        cd: $home/plugins
        cmd:
          - git clone https://github.com/discourse/docker_manager.git
  after_web_config:
    - replace:
        filename: /etc/nginx/nginx.conf
        from: /sendfile.+on;/
        to: |
          server_names_hash_bucket_size 64;
          sendfile on;
    - file:
        path: /etc/nginx/conf.d/discourse_redirect_1.conf
        contents: |
          server {
            listen 443;
            server_name example.com;
            return 301 $scheme://www.example.com$request_uri;
          }
  after_ssl:
    - replace:
        filename: "/etc/runit/1.d/letsencrypt"
        from: /-k 4096 -w \/var\/www\/discourse\/public/
        to: |
          -d www.example.com -d example.com -k 4096 -w /var/www/discourse/public
    - replace:
        filename: "/etc/runit/1.d/letsencrypt"
        from: /-k 4096 --force -w \/var\/www\/discourse\/public/
        to: |
          -d www.example.com -d example.com -k 4096 --force -w /var/www/discourse/public
    - replace:
        filename: "/etc/nginx/conf.d/discourse.conf"
        from: /return 301 https.+/
        to: |
          return 301 https://$host$request_uri;
    - replace:
        filename: "/etc/nginx/conf.d/discourse.conf"
        from: /gzip on;[^\}]+\}/m
        to: |
          gzip on;
          add_header Strict-Transport-Security 'max-age=31536000'; # remember the certificate for a year and automatically connect to HTTPS for th$
as always, remember that spacing and indentation is extremely important in the app.yml file. After you’ve done editing, you have to rebuild the container with:
cd /var/discourse
./launcher rebuild app