Why should Meteor MUP Setup behave different in private network

Question

I have a Ubuntu 18.04 Server VM with a public ip and also another VM in the private network (I am also located in the private network and can ssh into the server; no VPN involved).

I have pushed dozens of Meteor 1.8.1 apps to our public VMs without any issues using the same process:

• mup init
• config mup.js and settings.json
• mup setup
• mup deploy

Now when I use the private-located VM (ip 10.x.y.z) then I get the following error on mup setup:

$ meteor mup setup 

Started TaskList: Setup Docker
[10.x.y.z] - Setup Docker
[10.x.y.z] x Setup Docker: FAILED

              ------------------------------------STDERR------------------------------------
              sudo: docker: command not found
        sudo: docker: command not found
        debconf: unable to initialize frontend: Dialog
        debconf: (Dialog frontend will not work on a dumb terminal, an emacs shell buffer, or without a controlling terminal.)
        debconf: falling back to frontend: Readline
        debconf: unable to initialize frontend: Readline
        debconf: (This frontend requires a controlling tty.)
        debconf: falling back to frontend: Teletype
        dpkg-preconfigure: unable to re-open stdin: 
        usermod: group 'docker' does not exist

Where the line Dialog frontend will not work on a dumb terminal, an emacs shell buffer, or without a controlling terminal makes me curious, since this should not be caused due to being in a private network, am I right?

mup.js is

module.exports = {
  servers: {
    one: {
      host: '10.x.y.z',
      username: 'root'
    }
  },

  app: {
    name: 'appname',
    path: '../',

    servers: {
      one: {},
    },

    buildOptions: {
      serverOnly: true,
    },

    env: {
      ROOT_URL: 'https://ref.to.domain.tld',
      MONGO_URL: 'mongodb://localhost/meteor',
      MONGO_OPLOG_URL: 'mongodb://mongodb/local',
      HTTP_FORWARDED_COUNT: 1,
      port: 12345
    },

    docker: {
      image: 'abernix/meteord:node-8.15.1-base',
    },

    // Show progress bar while uploading bundle to server
    // You might need to disable it on CI servers
    enableUploadProgressBar: true
  },

  mongo: {
    version: '3.4.1',
    servers: {
      one: {}
    }
  },

  // (Optional)
  // Use the proxy to setup ssl or to route requests to the correct
  // app when there are several apps

  proxy: {
    domains: 'ref.to.domain.tld',
    ssl: {
      forceSSL: true,
      letsEncryptEmail: '[email protected]'
    },
    clientUploadLimit: '50M'
  }
};

Why is this? I can't get a reason for why it should behave so different while the VM does not differ besides the network config?