It would only take about an hour or so to update the Armory website so that it would include up-to-date and complete instructions for installing on various OSes, in order to avoid scaring off new users (who might be willing and able to install Ubuntu - but could get stopped dead in their tracks due to the outdated / incomplete GPG-verification instructions on the Armory website, and the lack of a one-line instruction saying how to install a deb file on Ubuntu).
After all the great work you've done on Armory, it would be pity to alienate potential new users simply due to failure to add a couple of paragraphs to the website.
Not sure, but it's possible that Armory have organised their Git repo to allow you to make a pull request for your suggested changes yourself. Anyone at ATI?
In addition, I'm not sure if I understand the problem you were having; I used dpkg-sig to verify an Armory package a few months ago for 93.1 or 93.2, and it worked after a little cajoling (although I was using Debian, not Ubuntu). In doing that, I seem to remember also that it is easier to just use gpg -v .asc than attempting to get dpkg-sig working.