Ubuntu 19.10 upgrade to 20.04 (out of date)

Question

There appears to be multiple issues with my attempt to upgrade. I tried following instructions from https://help.ubuntu.com/community/EOLUpgrades because my 19.10 is no longer supported. I should mention my computer skills are extremely limited. I don't know a lot about terminal other than copy/paste, so if instructions aren't clear or assume I know to add symbols or something I am not going to figure it out. When I run sudo apt-get update this is what I receive:

E: The repository 'http://us.archive.ubuntu.com/ubuntu disco Release' does not 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 disco-updates Release' does not 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 disco-backports Release' does not 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://security.ubuntu.com/ubuntu disco-security Release' does not 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: GPG error: http://dl.google.com/linux/earth/deb stable Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 78BD65473CB3BD13
E: The repository 'http://dl.google.com/linux/earth/deb stable Release' is not signed.
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.

I am sure everything I need to know is written right in there, but for the life of me I cannot figure out what to do. I tried looking things up and ran into many issues and instead of listing all that here it might be best if I start from the beginning. If someone could PLEASE help me figure this out so I can update...

Re-ran the update command after following a suggested article. This is what I receive now:

Get:1 http://security.ubuntu.com/ubuntu eoan-security InRelease [97.5 kB]
Hit:2 http://us.archive.ubuntu.com/ubuntu eoan InRelease                       
Hit:3 http://archive.canonical.com/ubuntu disco InRelease                      
Ign:4 http://us.archive.ubuntu.com/ubuntu disco InRelease                      
Ign:5 http://dl.google.com/linux/earth/deb stable InRelease                    
Get:6 http://us.archive.ubuntu.com/ubuntu eoan-updates InRelease [97.5 kB]
Ign:7 http://security.ubuntu.com/ubuntu disco-security InRelease               
Err:8 http://security.ubuntu.com/ubuntu disco-security Release
  404  Not Found [IP: 2001:67c:1562::15 80]
Hit:9 http://dl.google.com/linux/earth/deb stable Release 
Ign:10 http://us.archive.ubuntu.com/ubuntu disco-updates InRelease
Get:11 http://us.archive.ubuntu.com/ubuntu eoan-backports InRelease [88.8 kB]
Ign:12 http://us.archive.ubuntu.com/ubuntu disco-backports InRelease
Err:13 http://us.archive.ubuntu.com/ubuntu disco Release
  404  Not Found [IP: 91.189.91.38 80]
Err:14 http://us.archive.ubuntu.com/ubuntu disco-updates Release
  404  Not Found [IP: 91.189.91.38 80]
Err:15 http://us.archive.ubuntu.com/ubuntu disco-backports Release
  404  Not Found [IP: 91.189.91.38 80]
Hit:17 http://ppa.launchpad.net/nemh/systemback/ubuntu xenial InRelease
Hit:18 http://ppa.launchpad.net/webupd8team/y-ppa-manager/ubuntu eoan InRelease
Reading package lists... Done
E: The repository 'http://security.ubuntu.com/ubuntu disco-security Release' does not 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 disco Release' does not 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 disco-updates Release' does not 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 disco-backports Release' does not 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.
N: Skipping acquire of configured file 'main/binary-i386/Packages' as repository 'http://dl.google.com/linux/earth/deb stable InRelease' doesn't support architecture 'i386'

Answer 1

PPAs (and repositories in general) correspond to specific versions of Ubuntu. If you, for example, run Ubuntu 19.10 Eoan Ermine and add a PPA to your list of repositories, the Eoan version of the PPA is added. That's so the packages from the PPA are compatible to your overall system.

If you then later upgrade to a different version of Ubuntu, that matching is "broken". Therefore, all third-party repositories are disabled in the upgrade process. You need to go through the list and adjust them manually.

Say, for example, you've got a PPA for Eoan. Then you need to check whether that PPA is also available for your new Ubuntu version. Not all repositories support every Ubuntu version. If it is supported, you need to change the code name in your list, for example from eoan to fossa, so you get the packages for the correct Ubuntu version again. It looks like there's some disco stuff from Ubuntu 19.04 Disco Dingo around as well, so you need to handle those, too.

Some repositories don't use the Ubuntu code names, especially those offering packages to multiple distributions (for example, Debian and Ubuntu). With those, you need to look into how the specific repository handles things.

For at least one of the repositories in your list you also need to renew the public key. Packages in a repository can be cryptographically signed. To check those signatures, your system needs the public key of the repository in question. Those keys have kind of a "shelf life", they expire after a certain date, and you need to get the new key that replaces the old. The details on this topic would be out of the scope of this answer, but you'd want to read up on the apt-key command.