Comment 7 for bug 1549300

What are you talking about? There is no point that dialog is not supported on Ubuntu ppc64el server!

In fact, dialog package is available by default in apt archive repository: http://us.ports.ubuntu.com/ubuntu-ports, in the same main URL as dash's:
http://us.ports.ubuntu.com/ubuntu-ports/pool/main/d/dialog/dialog_1.2-20150920-1ubuntu1_ppc64el.deb
http://us.ports.ubuntu.com/ubuntu-ports/pool/main/d/dash/dash_0.5.8-2.1ubuntu2_ppc64el.deb

for quick installation for all Ubuntu releases up to 16.04 (Xenial Xerus) so far, as demonstrated below:

root@ubt1604KD2:/# uname -a
Linux ubt1604KD2 4.4.0-15-generic #31-Ubuntu SMP Fri Mar 18 19:06:23 UTC 2016 ppc64le ppc64le ppc64le GNU/Linux

root@ubt1604KD2:~# apt install dialog
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following NEW packages will be installed:
  dialog
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 199 kB of archives.
After this operation, 1,311 kB of additional disk space will be used.
Get:1 http://us.ports.ubuntu.com/ubuntu-ports xenial/main ppc64el dialog ppc64el 1.2-20150920-1ubuntu1 [199 kB]
Fetched 199 kB in 0s (255 kB/s)