Cannot update - PPAs do not have release files

Question

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.
E: The repository 'http://ppa.launchpad.net/noobslab/icons2/ubuntu bionic 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.
E: The repository 'http://ppa.launchpad.net/ravefinity-project/ppa/ubuntu bionic 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

It simply means that these two repositories have not yet been updated for 18.04. You could try editing /etc/apt/sources.list to replace bionic with artful or whatever is the latest version shown.

If you click on your links in the question and then click dists, you will see which versions are available.