If you look at the script:
It installs Klipper on an rPi which has Octopi running on it - if you read through it, you’ll see that the script itself uses resources that Octopi loaded in for its use (ie Python 2.7).
If you look at the Klipper master scripts repository:
You’ll see that the last time there was updates made to install-octopi.sh was four years ago (by Kevin). Since then (actually just less than four years ago) Klipper migration to Python 3.* started: Upcoming v0.10.0 Release
Based on these dates and the fact that you seem to be the first person who has issue with install-octopi.sh that I can find, I don’t think it’s a viable method for installing Klipper with Octopi.
As I am writing this post, I see that @EddyMI3D has provided you with a basic installation and connection workflow for using Octopi with Klipper.
This will undoubtedly be the most expedient way for you to get the two software packages working together.