How can I solve "The repository 'cdrom://Ubuntu 20.04.2.0 LTS _Focal Fossa_ - Release amd64 (20210209.1) focal Release' does not have a Release file"?

Question

$ sudo apt update
E: The repository 'cdrom://Ubuntu 20.04.2.0 LTS _Focal Fossa_ - Release amd64 (20210209.1) focal Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

Answer 1

Open Software & Updates, in the Ubuntu Software tab, uncheck Cdrom with Ubuntu 20.04 'Focal Fossa' under Installable from CD-ROM/DVD