How to use Codeigniter with other framework?

1. Install "codeigniter4/framework" via Composer.
2. add dependencies (constants, functions, etc.) in somewhere when needed.

Let me try another time. Suppose you want to use CI4 in another framework that does not support composer autoloader. I am a noob at this. But I can understand that there are class path that I can use. But I don't know the class names or the namespaces. Have you heard of Eloquent from Laravel. We can use this independently anywhere.