After following the instructions for adding the PPA to my local system, I encounter the following message from the output of apt update:
Err:36 http://ppa.launchpad.net/numix/ppa/ubuntu jammy InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 52B709720F164EEB
Hit:38 http://ppa.launchpad.net/ubuntu-mozilla-daily/ppa/ubuntu jammy InRelease
Reading package lists... Done
W: GPG error: http://ppa.launchpad.net/numix/ppa/ubuntu jammy InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 52B709720F164EEB
E: The repository 'http://ppa.launchpad.net/numix/ppa/ubuntu jammy 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.
The system is Linux Mint 21, which is based on Ubuntu 22.04 (jammy).
After following the instructions for adding the PPA to my local system, I encounter the following message from the output of
apt update
:The system is Linux Mint 21, which is based on Ubuntu 22.04 (
jammy
).