NextCloud on Synology - issue with proxy / SSL

Hello

Pretty new here so please bear with me if I am not doing this “by the book”…

I am trying to deploy the Nextcloud docker on a Synology NAS.

Here is the docker-compose.yml I used:

version: '3' 

services:

  proxy:
    image: jwilder/nginx-proxy:alpine
    labels:
      - "com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy=true"
    container_name: nextcloud-proxy
    networks:
      - nextcloud_network
    ports:
      - 8080:80
      - 4443:443
    volumes:
      - ./proxy/conf.d:/etc/nginx/conf.d:rw
      - ./proxy/vhost.d:/etc/nginx/vhost.d:rw
      - ./proxy/html:/usr/share/nginx/html:rw
      - ./proxy/certs:/etc/nginx/certs:ro
      - /etc/localtime:/etc/localtime:ro
      - /var/run/docker.sock:/tmp/docker.sock:ro
    restart: unless-stopped
  
  letsencrypt:
    image: jrcs/letsencrypt-nginx-proxy-companion
    container_name: nextcloud-letsencrypt
    depends_on:
      - proxy
    networks:
      - nextcloud_network
    volumes:
      - ./proxy/certs:/etc/nginx/certs:rw
      - ./proxy/vhost.d:/etc/nginx/vhost.d:rw
      - ./proxy/html:/usr/share/nginx/html:rw
      - /etc/localtime:/etc/localtime:ro
      - /var/run/docker.sock:/var/run/docker.sock:ro
    restart: unless-stopped

  db:
    image: mariadb
    container_name: nextcloud-mariadb
    networks:
      - nextcloud_network
    volumes:
      - db:/var/lib/mysql
      - /etc/localtime:/etc/localtime:ro
    environment:
      - MYSQL_ROOT_PASSWORD=xxxxx
      - MYSQL_PASSWORD=xxxx
      - MYSQL_DATABASE=nextcloud
      - MYSQL_USER=nextcloud
    command: --transaction-isolation=READ-COMMITTED --binlog-format=ROW
    restart: always
  
  app:
    image: nextcloud:latest
    container_name: nextcloud-app
    networks:
      - nextcloud_network
    depends_on:
      - letsencrypt
      - proxy
      - db
    volumes:
      - nextcloud:/var/www/html
      - ./app/config:/var/www/html/config
      - ./app/custom_apps:/var/www/html/custom_apps
      - ./app/data:/var/www/html/data
      - ./app/themes:/var/www/html/themes
      - /etc/localtime:/etc/localtime:ro
    environment:
      - VIRTUAL_HOST=nextcloud.domain.tld
      - LETSENCRYPT_HOST=nextcloud.domain.tld
      - LETSENCRYPT_EMAIL=me@domain.tld
    restart: unless-stopped

volumes:
  nextcloud:
  db:
  
networks:
  nextcloud_network:

which, amazingly enough, yielded a working instance on port 8080.
However I’m having issues accessing via SSL (on port 4443) and generating a let’s encrypt cert.

Any advise / guidance most welcome.