N: Missing Signed-By in the sources.list(5) entry for 'http://mirrors.digitalocean.com/ubuntu'

Hey!

Can you share the contents of your /etc/apt/sources.list.d/ubuntu.sources file?

cat /etc/apt/sources.list.d/ubuntu.sources

I just created a new Ubuntu 24.04 server and the DigitalOcean mirror definition in that file is as follows:

## See the sources.list(5) manual page for further settings.
Types: deb
URIs: http://mirrors.digitalocean.com/ubuntu/
Suites: noble noble-updates noble-backports
Components: main universe restricted multiverse
Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg

## Ubuntu security updates. Aside from URIs and Suites,
## this should mirror your choices in the previous section.
Types: deb
URIs: http://security.ubuntu.com/ubuntu
Suites: noble-security
Components: main universe restricted multiverse
Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg

Does this match your configuration as well?

On a side note, pne thing to keep in mind is that whenever doing such large OS upgrades it is best to have a snapshot of your Droplet. That way in case of anything going wrong, you can restore back to a working version of your server.

Ideally, I think the safest path that maximizes speed is to make a snapshot, make a duplicate Droplet from it, do the upgrade on the duplicated Droplet. If it works, then you can decide how important that IP and uptime is to you and either stick with the new one or upgrade the old one.

If the upgrade does not work well, you know to set aside some time and then do a migration as discussed here:

https://www.digitalocean.com/community/questions/easy-restart-question?comment=202501

- Bobby