here should be a standard where motherboards read GPU temperatures and allow it to be used in the BIOS fan curves. The only reliable way I know of right now to control case fan speed with GPU temperature is using paid software (Argus Monitor), which even if it was free would be another program running in the background.
GPUs tend to be the most heat-producing components in the system. CPU temperature isn’t a good substitute - CPUs can be at a much lower temperature when the GPU is going full blast and much higher temperature when the GPU is idle.
It just seems like a very obvious shortcoming in the quest to optimize noise and airflow. https://egp.cnv.to/usd/69