I was able to install Version 3.0.1 on Debian 10. I tried a number of times with Ubuntu 18.04 LTS with no luck.
try this just doing a reinstall myself
apt install gnupg curl wget htop iftop
wget --output-document=/etc/apt/sources.list.d/bluecherry-bionic.list http://unstable.bluecherrydvr.com/sources.list.d/bluecherry-bionic.list
apt install bluecherry/bionic
it should work
there is a bug in the installer script where its get a blank / empty .list file