I am using 18.04 version. i wanted to install game war zone 2100 so i installed its dependencies and after that i am getting this error. i cannot update the software center is not opening . the synaptic package manager is also not opening. On the status bar the red minus icon appears as a error. i even cant upgrade. the apt update gives me this error.
Reading package lists... Done
E: Failed to fetch http://ppa.launchpad.net/webupd8team/popcorntime/ubuntu/dists/trusty/InRelease 403 Forbidden [IP: 91.189.95.83 80]
E: The repository 'http://ppa.launchpad.net/webupd8team/popcorntime/ubuntu trusty InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The value 'xenial' is invalid for APT::Default-Release as such a release is not available in the sources
trusty
(14.04) andxenial
(16.04) PPAs in 18.04? – muru Apr 16 '20 at 06:55