Yep, I check in from time to time
I recall someone wanting to try my controller with a BMW fan, but I never heard back if it worked or not.
As noted, there are two main styles of fans.
"Dumb" fans, with only power and ground wires, and no built in computer. Apply power and they turn on to full speed. Controllers for these need to interrupt the power to control the fan speed.
"Smart" fans, with power, ground, one or more control lines, and a built in computer. Input a PWM at the right frequency to the control line, and the built in computer will then control the fan to the commanded speed.