sudo vim /etc/apt/sources.list.d/kylin.list
Add the following code:
deb http://ppa.launchpad.net/kelleyk/emacs/ubuntu focal main
deb http://archive.ubuntukylin.com:10006/ubuntukylin bionic main
deb http://archive.ubuntukylin.com:10006/software-focal focal main
deb http://archive.ubuntukylin.com:10006/software focal main
deb http://archive.ubuntukylin.com:10006/ubuntu focal main
deb http://archive.ubuntukylin.com/ubuntukylin focal-partner main
after saving
sudo apt update
That's it.
An error occurred
Solution:
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys D259B7555E1D3C58
(This is based on your own filling)
successfully resolved
sudo apt update
sudo apt upgrade