gsmartconrtrol missing in repositories

Run:

apt-cache policy gsmartcontrol

On the ones it is installed on. Make sure that repository is enabled on the one it won't install on.

gsmartcontrol is in the universe repository.
https://launchpad.net/ubuntu/+source/gsmartcontrol

Maybe you haven't activated the universe repository on the affected system.

On the system with the problem:

ea@Discovery:~$ sudo apt-cache policy gsmartcontrol
[sudo] password for ea:
gsmartcontrol:
  Installed: (none)
  Candidate: (none)
  Version table:
ea@Discovery:~$

The no problem system:

ea@seanix:~$ sudo apt-cache policy gsmartcontrol
[sudo] password for ea:
gsmartcontrol:
  Installed: 1.1.3-1
  Candidate: 1.1.3-1
  Version table:
 *** 1.1.3-1 500
        500 http://ca.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages
        100 /var/lib/dpkg/status
ea@seanix:~$

I compared the "Software & Updates" from the affected and the not affected systems, and found the "universe" not checked on the affected system.
Put a check mark in the proper box which resulted in the fix., an update was run and the installation succeeded.

Thank you Gentlemen for your help

Why are you adding sudo to the apt-cache command? If a command needs sudo I will add it. It doesn't so I didn't add it.

Too many times I did not add sudo and was told to use it, I add it just to be sure.
I will keep your suggestion in mind.

Remember, I own these systems and am the only user, I also understand the power of sudo, and am very careful with it.

Again thanks for the help and reminder

EA

If you are adding "sudo" to commands that do not need it, then you are not very careful with it.

Point taken, I will henceforward try commands without sudo until I am told that I need it. Never too old to learn...

Rule of thumb:
If it is a command that _changes_ something in the system area or that needs to access data which are worth being kept secret, then it needs sudo.
If it is a command that only _reads_ admin data which are publicly available (like list of installed software), then user rights without sudo should be sufficient.

Copied the above to a document for future reference.

Thank you.