Maybe this will help someone. I'm using the following and it works in our GitHub Enterprise:

name: "Bootstrap Terraform State"
run-name: "${{ github.event.inputs.operation == 'init' && format('Provision') || format('Destroy') }} terraform state for the customer ${{ github.event.inputs.customer_name}}. Branch: ${{ github.ref_name }} and msg: ${{ github.event.head_commit.message}}"
on:
  workflow_dispatch:
    inputs:
      operation:
 ...

Cheers