Ubuntu 22 GPG error: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY

Symptoms

When installing new software or running package updates, Ubuntu's package manager flags the following error on one or more repos:

The following signatures couldn't be verified because the public key is not available: NO_PUBKEY $pubkey_value

Description

This error occurs when the public key for the repo is not imported into your server's package manager. The "$pubkey_value" will change depending on the repo that is triggering the error.

Workaround

1. Access the server's command line as the 'root' user via SSH or "Terminal" in WHM.
2. Use the apt-key tool to import the public key reflected in the error:

   apt-key adv --keyserver keyserver.ubuntu.com --recv-keys $pubkey_value