openrepo VS apt-offline

I'd probably deploy an internal apt repo like OpenRepo or something similar

Yes, it does. Functionality works fine in an offline silo. I just added this commit a few minutes ago to improve the way the login page works when the browser has no internet access: https://github.com/openkilt/openrepo/commit/d8d8b9bfb46f716e1144cedd74e04b9c63101088

I just released an open source project called OpenRepo:https://github.com/openkilt/openrepo

If you have a USB stick and access to a Windows computer (neighbours, friends, etc.) with Internet access, you can use https://github.com/rickysarraf/apt-offline for this.

Take a look at https://github.com/rickysarraf/apt-offline

One possibility would be http://rickysarraf.github.io/apt-offline/. With this tool you can copy the necessary packages, including their dependencies, to a USB stick and then install them on a computer without internet access.

There was apt-offline that did a very good job as far as that goes.

Check out apt-offline which is packaged for Ubuntu.

I have also seen apt-offline.

Here's the discussion about the "ERROR: Path for keyring invalid" problem with apt-offline: https://github.com/rickysarraf/apt-offline/issues/102

If you cannot establish another network connection, you could solve the problem by using https://github.com/rickysarraf/apt-offline. You will need a Debian based distribution with internet access (a live distribution should probably work) and an USB Stick. This will copy the required package including dependencies to a USB stick. With this you can install the package on the computer without internet connection.