Does anyone have examples of a ScriptRunner custom listener on how to change the issuetype on the creation of the ticket?
In this case, it will be IF the ticket is created with a certain issuetype AND the description contains certain data.
Changing issue type with any sort of automation is never a good idea except for the very rare case that the issue type has the same field configuration and workflow.
That's why the Move action is built like a wizard. There are many steps and decisions that have to be made along the way. That's difficult to predict in a script.
What I would suggest for your use case is a behaviour that raises an error if the description contains keywords that don't match the selected issue type.
Something like "based on this description, it appears that you want to raise a X issue type, but you have selected Y, please select Y or specify a description that's more in line with X"