Disclaimer: Please follow this guide being aware of the fact that I'm not an expert regarding the things outlined below, however I made my best attempt.
NVIDIA driver since version 435.17 supports this method. xf86-video-modesetting, xf86-video-amdgpu (450.57), and xf86-video-intel (455.38) are officially supported as iGPU drivers.
For Turing generation cards with Intel Coffee Lake or above CPUs (as well as the Ryzen 5800H Acer Nitro 5 that im using maybe other ryzens too?), it is possible to fully power down the GPU when not in use.
nvidia gpus 1650 and up is supposedly working with this?.