Hmm. I guess I have no idea how this chip interfaces with the kernel then? The only knobs that seem to be documented to exist ever are direct RPM controls for manual control.
I know it's possible (despite the insistence to the contrary on the other thread), as basically every laptop does it. Only do desktops seem to struggle with this concept.
How fan control is configured depends on the SuperIO chip, so it's different for eg. Fintek SuperIOs than for Winbond/Nuvoton SuperIOs.
On Linux, a supported SuperIO will be exposed as a directory under /sys/class/hwmon. On one of my systems, the SuperIO is a Nuvoton NCT6791, so the relevant driver documentation is https://www.kernel.org/doc/Documentation/hwmon/nct6775
Relevant sysfs files to note are pwm[1-7]_mode to toggle between DC voltage and PWM control, and pwm[1-7]_enable to switch between full speed, pure software speed control, and several Nuvoton-specific automatic speed control modes.
I know it's possible (despite the insistence to the contrary on the other thread), as basically every laptop does it. Only do desktops seem to struggle with this concept.