I am trying to install Lyx via ppa in Ubuntu 18.04. I tried following the instructions here and added the ppa. It is giving the following error message:
arpan@arpan-laptop:~$ sudo add-apt-repository ppa:lyx-devel/release
[sudo] password for arpan:
Look here for updated release versions of LyX.
More info: https://launchpad.net/~lyx-devel/+archive/ubuntu/release
Press [ENTER] to continue or Ctrl-c to cancel adding it.
'Error reading https://keyserver.ubuntu.com/pks/lookup?op=get&options=mr&exact=on&search=0xEDE9A1109EB3355B591159DCA64833C9F8214ACD: [Errno -2] Name or service not known'
After this when I try doing apt update, I again get a similar error:
W: GPG error: http://ppa.launchpad.net/lyx-devel/release/ubuntu bionic InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A64833C9F8214ACD
E: The repository 'http://ppa.launchpad.net/lyx-devel/release/ubuntu bionic 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.
