Use the following to set up Nextcloud in a Docker Container:

version: '3.9'
services:
  mariadb:
    image: mariadb:latest
    container_name: Nextcloud-DB
    security_opt:
      - no-new-privileges:true
    command: --transaction-isolation=READ-COMMITTED --binlog-format=ROW --innodb-read-only-compressed=OFF
    environment:
      - PUID=1000
      - PGID=1000
      - MYSQL_ROOT_PASSWORD=[PASSWORD]
      - MYSQL_PASSWORD=[PASSWORD]
      - MYSQL_DATABASE=nextcloud
      - MYSQL_USER=nextcloud
      - TZ=America/Los_Angeles
    volumes:
      - /volume1/docker/nextcloud/mariadb:/config
    restart: on-failure:5

  redis:
    image: redis:latest
    container_name: Nextcloud-REDIS
    hostname: nextcloudredis
    healthcheck:
      test: ["CMD-SHELL", "redis-cli ping || exit 1"]
    environment:
      - PUID=1000
      - PGID=1000
      - TZ=America/Los_Angeles
    volumes:
      - /volume1/docker/nextcloud/redis:/data:rw
    restart: on-failure:5

  nextcloud:
    image: nextcloud:latest
    container_name: Nextcloud
    ports:
      - 9333:80
    depends_on:
      mariadb:
        condition: service_started
      redis:
        condition: service_healthy
    healthcheck:
      test: curl -f http://localhost:80/ || exit 1
    environment:
      - REDIS_HOST=nextcloudredis
      - NEXTCLOUD_TRUSTED_DOMAINS=[DOMAIN] 10.0.1.9
      - TRUSTED_PROXIES=[DOMAIN] 10.0.1.9
      - OVERWRITEHOST=[DOMAIN]
      - OVERWRITEPROTOCOL=https
      - MYSQL_PASSWORD=[PASSWORD]
      - MYSQL_DATABASE=nextcloud
      - MYSQL_USER=nextcloud
      - MYSQL_HOST=mariadb
    volumes:
      - /volume1/docker/nextcloud/html:/var/www/html:rw
      - /volume1/docker/nextcloud/custom_apps:/var/www/html/custom_apps:rw
      - /volume1/docker/nextcloud/config:/var/www/html/config:rw
      - /volume1/docker/nextcloud/data:/var/www/html/data:rw
      - /volume1/docker/nextcloud/themes:/var/www/html/themes:rw
    restart: on-failure:5

  cron:
    image: nextcloud:apache
    container_name: Nextcloud-CRON
    restart: always
    volumes:
      - /volume1/docker/nextcloud/config:/var/www/html/config:rw
      - /volume1/docker/nextcloud/html:/var/www/html:rw
      - /volume1/docker/nextcloud/custom_apps:/var/www/html/custom_apps:rw
      - /volume1/docker/nextcloud/data:/var/www/html/data:rw
    entrypoint: /cron.sh
    depends_on:
      mariadb:
        condition: service_started
      redis:
        condition: service_started

  proxy:
    image: 'jc21/nginx-proxy-manager:latest'
    container_name: Nextcloud-PROXY
    restart: unless-stopped
    ports:
      - '80:80'
      - '81:81'
      - '443:443'
    volumes:
      - /volume1/docker/nextcloud/proxy/data:/data
      - /volume1/docker/nextcloud/proxy/letsencrypt:/etc/letsencrypt

Source

https://github.com/docker/awesome-compose/tree/master/nextcloud-redis-mariadb