Just to be sure (and because I had already a lot of dependencies installed on my machine) I tried with a fresh install of Ubuntu 20.04 on a new VritualBox VM.
I think you are missing a step in the README: before installing the i386 library packages, I'm quite sure you have to enable the i386 architecture.
So this is the sequence of commands I verified to be working on a fresh install:
$ sudo dpkg --add-architecture i386
$ sudo apt install libopenal1:i386 libglu1:i386 libxrandr2:i386
$ cd Zordak; ./start.sh (the script I wrote last time)
Hope this helps. Bye and keep up with the really good job you're doing.