see apt-secure(8) manpage for repository creation and user configuration details ubuntu 20.04 code example

Example: n see apt-secure(8) manpage for repository creation and user configuration details. ubuntu

wget -q "http://deb.playonlinux.com/public.gpg" -O - | sudo apt-key add -

sudo wget http://deb.playonlinux.com/playonlinux_trusty.list -O /etc/apt/sources.list.d/playonlinux.list

sudo sh -c "echo 'deb http://download.opensuse.org/repositories/home:/strycore/xUbuntu_16.04/ /' > /etc/apt/sources.list.d/lutris.list"

wget -nv https://download.opensuse.org/repositories/home:strycore/xUbuntu_16.04/Release.key -O Release.key

sudo apt-key add - < Release.key

sudo apt-get update