I wanted to install elementary+ icons, but got an error while trying to add devs PPA:
E: The repository 'http://ppa.launchpad.net/cybre/elementaryplus/ubuntu bionic Release' does not have a Release file. 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.
I tried various solutions I found but none of them worked. Can you please help?