That said, for what you are trying to do, I would investigate two paths:
1. use the plain Toolkit and try to bake your own image and install it manually. For this check the Elemental Toolkit docs:
https://rancher.github.io/elemental-toolkit/docs/
2. from a Rancher cluster, install Elemental and provision a child cluster. On that child cluster install Rancher 🤔 well, wouldn't make much sense honesty I guess