After a research at web, I was able to figure out the solution. There was 2 keys installed, one previous key installed in /etc/apt/trusted.gpg using apt-key, that expired on October 2023, and the other installed in /etc/apt/trusted.gpg.d using curl, that is valid. So when I tried to update, the apt update command detected the expired key. It happened because apt-key is now deprecated but I used it when I first installed SciDAVis at the computer.

The solution is: first, delete all hpcoder1 keys using apt-key:

$ sudo apt-key del 5606C8D03F9E5FB8

That will erase both keys from hpcoder1. Then install again only one key at the right place with

$ curl -fsSL https://download.opensuse.org/repositories/home:hpcoder1/xUbuntu_20.04/Release.key | gpg --dearmor | sudo tee /etc/apt/trusted.gpg.d/home_hpcoder1.gpg > /dev/null

Make sure you are using the correct version of Ubuntu, in my case it is Ubuntu 20.04.

After that, the apt update error messages disappear.

Best regards,

Rogério Nunes Wolff