First Solution:

apt purge ubuntu-advantage-tools

Source: https://askubuntu.com/a/1435437/647986

Second Solution:

sudo pro config set apt_news=false

Source:

• https://askubuntu.com/a/1457810/647986
• https://bugs.launchpad.net/ubuntu/+source/ubuntu-advantage-tools/+bug/1950692/comments/16

Third Solution:

# One option is to create a symbolic link for 20apt-esm-hook.conf to /dev/null:
sudo ln -s -f /dev/null /etc/apt/apt.conf.d/20apt-esm-hook.conf

# Another option is to just comment out the action lines in that file:
sudo sed -i'' -e 's/^\(\s\+\)\([^#]\)/\1# \2/' /etc/apt/apt.conf.d/20apt-esm-hook.conf

# Or a third option is to just rename that file to a 
# .bak file, and create a zero length file of the same name:
sudo mv /etc/apt/apt.conf.d/20apt-esm-hook.conf /etc/apt/apt.conf.d/20apt-esm-hook.conf.bak
sudo touch /etc/apt/apt.conf.d/20apt-esm-hook.conf

Source: https://askubuntu.com/a/1434762/647986

Other Resort

https://github.com/Skyedra/UnspamifyUbuntu