Ubuntu 14.04 is the only distribution supported by this script.
This script/repo has been deprecated in favor of managing and installing SIFT using saltstack. You must use 16.04 going forward to install SIFT using SaltStack or the SIFT CLI.
The preferred method of installation is done via the SIFT CLI tool. This command line utility will download and validate install signatures and SHA hashes before installing.
If you have bugs or issues to track please use https://github.com/sans-dfir/sift/issues