How to fix this error that blocks upgrading jammy -> noble?

Normal updates go through just fine, but the release-upgrade to the next LTS does not.

Fortunately, I'm using do-release-upgrade under the script(1) command, so I capture the output. It's too long to put the whole thing here. The short version is that there's a complaint about a GitHub credential, and then the upgrade backs out to the original state.

But there's another problem to mention first: the output suggests web pages for getting help on Ubuntu sites. But the one I looked at suggested using an app called 'xchat', but when I use the apt-get command suggested for installing it, the app does not appear to exist (in my Xubuntu Jammy). So gave up on the Ubuntu direct help, and I'm hoping for a better answer here.

I don't know why the problem occurs, or even what has actually gone wrong, so I could use help both with diagnosis and with a fix.

Here's the complaint with a little context:

Reading state information... Done
Get:1ahttps://cli.github.com/packageststablerInReleaseu[3,917[B]itingafornheaders]aders]]
Hit http://us.archive.ubuntu.com/ubuntuojammyrInReleaseu.com] [Waiting for headers]
Hit https://dl.google.com/linux/chrome/debestable.InReleasem] [Waiting for headers]
Err https://cli.github.com/packagesnstableeInReleaseuntu.com]
  The following signatures were invalid: EXPKEYSIG 23F3D4EA75716059 GitHub CLI <[email protected]>
```Reading state information... Done
Get:1ahttps://cli.github.com/packageststablerInReleaseu[3,917[B]itingafornheaders]aders]]
Hit http://us.archive.ubuntu.com/ubuntuojammyrInReleaseu.com] [Waiting for headers]
Hit https://dl.google.com/linux/chrome/debestable.InReleasem] [Waiting for headers]
Err https://cli.github.com/packagesnstableeInReleaseuntu.com]
  The following signatures were invalid: EXPKEYSIG 23F3D4EA75716059 GitHub CLI <[email protected]>

Then

Third party sources disabled

Some third party entries in your sources.list were disabled. You can
re-enable them after the upgrade with the 'software-properties' tool
or your package manager.

To continue please press [ENTER]

Then after some downloading, the failure is announced:

Hit[http://security.ubuntu.com/ubuntuonoble-security.InRelease125.190.80)]]
Hit[http://ppa.launchpad.net/system76-dev/stable/ubuntu noble InRelease
Fetchedk0nB]in 0s (0 B/s)

Error during update

A problem occurred during the update. This is usually some sort of
network problem, please check your network connection and retry.


Restoring original system state

I did not see a network problem. My usual test is "ping 8.8.8.8" which pings a Google server, is easy to remember, and seems a decent test of connectivity minus the domain-name servers.

So how do I find out what's really wrong and how to fix it?