Sorry about that, thanks for reporting the error. Until we can get a proper updated 64 bit version of the game up, this should get it running in ubuntu 20.04.
If you don't have it installed already, install steam from the ubuntu software manager. Once installed, run steam and allow it to go through the updates and everything until you get to the login prompt, this will create file paths that will be referenced in a moment. You don't need to login, and you can exit steam once you are at the login prompt.
On my system, I needed to also install the following libraries: