I have it sitting on a URL and I have an iOS share shortcut to throw any URL at it and it downloads the video.

Copy-paste from my ansible setup if you're interested, shouldn't be that hard to convert to docker-compose.

    - name: Build metube options separately, avoids inline JSON in metube setup
      ansible.builtin.set_fact:
        metube_ytdl_options:
          postprocessors:
            - key: FFmpegEmbedSubtitle
            - key: SponsorBlock
              categories:
                - sponsor
            - key: ModifyChapters
              remove_sponsor_segments:
                - sponsor
          subtitleslangs:
            - en
            - "-live_chat"
          verbose: true
          writeautomaticsub: true
          writesubtitles: true

    - name: Create metube container
      community.general.docker_container:
        container_default_behavior: "no_defaults"
        name: metube
        image: alexta69/metube:latest
        restart_policy: always
        env:
          UID: "{{ plex_userid }}"
          GID: "{{ docker_users_groupid }}"
          DELETE_FILE_ON_TRASHCAN: "false"
          DOWNLOAD_DIRS_INDEXABLE: "true"
          DOWNLOAD_DIR: /downloads
          TEMP_DIR: /metube-tmp
          STATE_DIR: /config
          TZ: "{{ timezone }}"
          YTDL_OPTIONS: "{{ metube_ytdl_options | to_json }}"
        mounts:
          - type: bind
            source: /stacks/metube/config
            target: /config
            read_only: false
          - type: volume
            source: metube_tmp_location_volume
            target: /metube-tmp
          - type: volume
            source: plex_metube_volume
            target: /downloads
        labels:
          "traefik.enable": "true"
          "traefik.http.routers.metube.middlewares": "authelia@docker"
          "traefik.http.routers.metube.service": "metube"
          "traefik.http.routers.metube-no-auth.rule": "Host(`metube.home.domain.com`) && (PathPrefix(`/favicon`) || PathPrefix(`/add`))"
          "traefik.http.routers.metube-no-auth.service": "metube"
          "traefik.http.services.metube.loadbalancer.server.port": "8081"
        ports: []
        dns_servers:
          - "{{ docker_network_ipv4_bridge_dns }}" # adguard
        networks:
          - name: bridge_ipv4