here is my configuration:

  letsencrypt: # https://github.com/linuxserver/docker-letsencrypt
    container_name: letsencrypt
    image: linuxserver/letsencrypt:latest
    restart: unless-stopped
    volumes:
    - /etc/localtime:/etc/localtime:ro
    - /srv/docker/letsencrypt:/config
    environment:
    - PGID=1000
    - PUID=1000
    - [email protected]
    - URL=xxx.duckdns.org
    - SUBDOMAINS=wildcard
    - VALIDATION=duckdns #http
    - TZ=Europe/London
    - DUCKDNSTOKEN=token
    ports:
    - "80:80"
    - "443:443"


  duckdns:
    container_name: duckdns
    image: linuxserver/duckdns
    restart: unless-stopped
    volumes:
    - /srv/docker/duckdns:/config
    environment:
    - PGID=1000
    - PUID=1000
    - SUBDOMAINS=xxx.duckdns.org
    - TOKEN=token
    - LOG_FILE=true
    - TZ=Europe/London
    ports:
    - "1480:80"
and this is my default file in /srv/docker/letsencrypt/nginx/site-confs/default

#### PORT 80 ACTIVE
server {
        listen 80;
        server_name xxx.duckdns.org;
        return 301 https://$host$request_uri;
}

# main server block
server {
        listen 443 ssl default_server;

        root /config/www;
        index index.html index.htm index.php;

        server_name xxx.duckdns.org;

        # enable subfolder method reverse proxy confs
        include /config/nginx/proxy-confs/*.subfolder.conf;

        # all ssl related config moved to ssl.conf
        include /config/nginx/ssl.conf;

        client_max_body_size 0;

        location / {
                try_files $uri $uri/ /index.html /index.php?$args =404;
        }
        location ~ \.php$ {
                fastcgi_split_path_info ^(.+\.php)(/.+)$;
                # With php7-cgi alone:
                fastcgi_pass 10.10.10.211:9001;
                #fastcgi_pass 127.0.0.1:9001;
                # With php7-fpm:
                #fastcgi_pass unix:/var/run/php7-fpm.sock;
                fastcgi_index index.php;
                include /etc/nginx/fastcgi_params;
        }
}

### HOMEASSISTANT
server {
        listen 443 ssl;

        root /config/www;
        index index.html index.htm index.php;

        server_name xxx.duckdns.org;

        include /config/nginx/ssl.conf;

        client_max_body_size 0;

        location / {
#               auth_basic "Restricted";
#               auth_basic_user_file /config/nginx/.htpasswd;
                proxy_set_header Host $host;
                proxy_redirect http:// https://;
                proxy_http_version 1.1;
                proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
                proxy_set_header Upgrade $http_upgrade;
                proxy_set_header Connection "upgrade";
                proxy_buffering               off;
                proxy_ssl_verify              off;
#               include /config/nginx/proxy.conf;
        }
}

# enable subdomain method reverse proxy confs
include /config/nginx/proxy-confs/*.subdomain.conf;
I have also forwarded port 80 to 80 and 443 to 443. when I go to my page i.e. https://xxx.duckdns.org I get the following :