sudo sh -c "echo deb http://dl.openfoam.org/ubuntu $VERS main > /etc/apt/sources.list.d/openfoam.list"
[sudo] password for george:
george@george-VirtualBox:~$ sudo apt-get update
Hit:1 http://security.ubuntu.com/ubuntu bionic-security InRelease
Hit:2 http://gr.archive.ubuntu.com/ubuntu bionic InRelease
Get:3 http://gr.archive.ubuntu.com/ubuntu bionic-updates InRelease [88,7 kB]
Get:4 http://gr.archive.ubuntu.com/ubuntu bionic-backports InRelease [74,6 kB]
Get:5 http://dl.openfoam.org/ubuntu bionic InRelease [6337 B]
Err:5 http://dl.openfoam.org/ubuntu bionic InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 6C0DAC728B29D817
Reading package lists... Done
W: GPG error: http://dl.openfoam.org/ubuntu bionic InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 6C0DAC728B29D817
E: The repository 'http://dl.openfoam.org/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.
george@george-VirtualBox:~$ sudo apt-get install openfoam170
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package openfoam170