This is really just a heads up as I found a solution.
Ok went back to the drawing board and this time decided to install via deb on a newish system.
I got the above error
a quick google search returned this
The way that worked for me was
wget http://mirrors.kernel.org/ubuntu/pool/main/libf/libffi/libffi6_3.2.1-8_amd64.deb sudo apt install ./libffi6_3.2.1-8_amd64.deb
I also needed to add numpy even though the deb didn’t ask for it.