As said, Eevee uses OpenGL, it is already using your GPU. There is no other option, it is not possible that Eevee is only using CPU only. I don’t know nvidia settings in Windows. If you have the display connected to the RTX card and you did not modify the nvidia settings, Eevee should be using the RTX card. Anyway, knowing which GPU is being used should be able to be detected with GPU-z.
You try heavy scenes at high samples. For example Mr. Elephant scene:
Thank you very much. My doubt is cleared.