Since January 2023, there have been some questions mentioning ESM Apps, that seem to have caused confusion among myself and others
On running sudo apt update, users will get a notification similar to this, stating that several packages from the universe repository have security updates that require Ubuntu Pro:

The following security updates require Ubuntu Pro with 'esm-apps' enabled:
  imagemagick libopenexr25 libmagick++-6.q16-8 libmagickcore-6.q16-6-extra
  libmagickwand-6.q16-6 imagemagick-6.q16 libmagickcore-6.q16-6
  imagemagick-6-common

To remove nag:

sudo mkdir /etc/apt/apt.conf.d/off;
sudo mv /etc/apt/apt.conf.d/20apt-esm-hook.conf 
/etc/apt/apt.conf.d/off;