apt-get update fails when updating from 17.04 to 17.10 after EOL, none of the mirrors can be found

I'm getting the following list of errors when trying any kind of apt-get commends. For example, sudo apt-get update eventually gives me

Reading package lists... Done
E: The repository 'http://us.archive.ubuntu.com/ubuntu zesty Release' does no longer have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://us.archive.ubuntu.com/ubuntu zesty-updates Release' does no longer have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.

N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://us.archive.ubuntu.com/ubuntu zesty-backports Release' does no longer have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: The repository 'http://us.archive.ubuntu.com/ubuntu zesty-security Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.

So there are a number of solutions here which involve changing to a different mirror, but that fails for me. I switch to the main server, no change. I ask the system to pick the best server for me, and I get a window "No suitable download server was found, check your internet connection". Well, I can ping google (and ask this question!), so it seems the internet is not the issue.

Anyone have any thoughts?

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 17.04
Release:    17.04
Codename:   zesty

The distribution is actually Pop!_OS, which I believe is just vanilla Ubuntu with particular software choices.

First we will fix your repositories :

sudo sed -i -re 's/([a-z]{2}\.)?archive.ubuntu.com|security.ubuntu.com/old-releases.ubuntu.com/g' /etc/apt/sources.list

This should adjust your /etc/apt/sources.list to look similar to this :

deb http://old-releases.ubuntu.com/ubuntu/ zesty-updates main

deb http://old-releases.ubuntu.com/ubuntu/ zesty-backports main

deb http://old-releases.ubuntu.com/ubuntu zesty-security main

deb http://old-releases.ubuntu.com/ubuntu zesty main universe restricted multiverse

Then run :

sudo apt-get update && sudo apt-get dist-upgrade