I tried to build the deb again and this line appears to break the build as it now returns nothing:

USER=`who | grep ':0' | grep -o '^\w*' | head -n1`

when this runs the USER variable remains empty which causes the package build to fail.

I modified mine to just set

USER=<My_UserName>

Which got it to work for me and I was able to install. See issue #28 for help with starting the service in 18.x by the way.