Recommended Design Pattern for a Simulator?

I am building an application that simulates a real piece of hardware. This hardware has a built in screen and has its own custom UI etc.

The requirements are that I should be able to build this application in such a way that I can switch out the front end UI frameworks if I so choose. For example I might use Unity and have the the piece of hardware be represented by a 3D model with a 2D UI or make it into a WPF application, or anything else.

The issue I am having a hard time distinguishing between what is the Model and the ViewModel / Controller.

In theory the entire simulator is modeling the piece of hardware and the way the UI behaves should be exactly the same despite what UI framework is used.

Basically, I am struggling with compartmentalizing what is considered the model, the view model, and the view.

Any suggestions regarding how to go about splitting this up in such a way would be welcome.