We don't provide ubuntu packages on the site as far as I can see, they are meant to work on a Debian.
The packages on the site have been built before the 18.04 release, so it is not surprising that they doesn't work on this version.
Probably we need to do something about this, but generally it is better to use distro provided packages. And if they don't work then you have to report this to the distro maintainers.