Missing libgnomeui-2.so.0 in Mint 20

I have a program (PageStream) that uses libgnomeui-2.so.0. I have read that it's considered "obsolete" and no longer included in Ubuntu 20.04, which Mint 20 is based on. Is there any way to install it, or will I have to revert to Mint 19 in order to run this program? I'm a user, not a programmer... I'm familiar enough with terminal and such to follow directions, just not to figure it out myself! It's obviously not in the normal Ubuntu 20.4/Mint20 repositories... This affects some other programs as well, none that I'm trying to run though... I found a few posts on the internet concerning this. I'm afraid I might get another related error after that one is fixed, but one at a time!

This is the script I'm using to run PageStream, and the error. I copied the script from a text file into terminal:

frank@frank-Linux-Mint-20:~$ cd PageStream5
frank@frank-Linux-Mint-20:~/PageStream5$ #!/bin/bash
frank@frank-Linux-Mint-20:~/PageStream5$ export PGSPATH=`dirname "$0"`
frank@frank-Linux-Mint-20:~/PageStream5$ export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$PGSPATH/SoftLogik/lib
frank@frank-Linux-Mint-20:~/PageStream5$ export PATH=$PATH:$PGSPATH
frank@frank-Linux-Mint-20:~/PageStream5$ $PGSPATH/PageStream5
./PageStream5: error while loading shared libraries: libgnomeui-2.so.0: cannot open shared object file: No such file or directory
frank@frank-Linux-Mint-20:~/PageStream5$ exit 0