Jordan the author of JS8Call suggested using the API to do this.
I decided to see what was around and found this well documented js8net API library, with that I was able to interact with the API from the command line, and could read and set the frequency.
Python is not something I'm familiar with, so I used ChatGPT to help me write a python script that would cycle through a list of frequencies changing to the next one every few minutes.
The result was JS8BandHop, a fairly simple Python script.