Ubuntu PPA is broken
In the readme there are instructions for adding the PPA:
You can add the this PPA. It gets automatically rebuild every day.
sudo add-apt-repository ppa:shortwave-developers/shortwave-nightly sudo apt update sudo apt install shortwave
I get the following error:
E: The repository 'http://ppa.launchpad.net/shortwave-developers/shortwave-nightly/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.