#Ubuntu 20.04 and 18.04
sudo nano /etc/apt/sources.list
# Add code in the list file
deb http://download.webmin.com/download/repository sarge contrib
# Ctrl + O for save and Ctrl + X for Exit
wget http://www.webmin.com/jcameron-key.asc
sudo apt-key add jcameron-key.asc
sudo apt update
sudo apt install webmin
# If you have Firewall Allow port 10000 to UFW
sudo ufw allow 10000