Since our friends at Ubuntu Cinnamon were interested in using the Ubuntu Unity ISO builder for Ubuntu Cinnamon, we are publishing the ISO builder for anyone to use it for building remix ISOs. We’ve set up a SourceForge project for it at https://sourceforge.net/projects/ubuntu-remixes/. As an example, we have built the Ubuntu MATE and Ubuntu Cinnamon ISOs based on impish using the builder. If anyone is interested in using it for developing new remixes as well, please check the wiki at https://sourceforge.net/p/ubuntu-remixes/wiki/Home/.
For support, join our Telegram group at https://t.me/ubunturemixes