root@pihole:/home/james# apt-get --yes --no-install-recommends install dialog dhcpcd5
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package dialog is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'dialog' has no installation candidate
E: Unable to locate package dhcpcd5
root@pihole:/home/james#
That doesn't look like we can currently support Ubuntu 18.04.1 with the current installer. We'll have to look at that platform and see what needs to be adjusted to be able to install and operate on that release.