I get the following error when checking for updates:
Err:18 http://ppa.launchpad.net/wireguard/wireguard/ubuntu bionic InRelease
403 Forbidden [IP: 91.189.95.83 80]
Hit:19 http://ppa.launchpad.net/xuzhen666/gnome-mpv/ubuntu bionic InRelease
Reading package lists... Done
E: Failed to fetch http://ppa.launchpad.net/wireguard/wireguard/ubuntu/dists/bionic/InRelease 403 Forbidden [IP: 91.189.95.83 80]
E: The repository 'http://ppa.launchpad.net/wireguard/wireguard/ubuntu bionic InRelease' is no longer 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.