cannot install on ubuntu 19.04

[roadh0use]

running sudo apt-add-repository "https://dl.bintray.com/chadsr/nordnm-deb main" gives the following error on ubuntu 19.04:
Err:13 https://dl.bintray.com/chadsr/nordnm-deb disco Release 404 Not Found [IP: 52.35.37.1 443] Reading package lists... Done E: The repository 'https://dl.bintray.com/chadsr/nordnm-deb disco 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.