I have run jetson_clocks and I have echoed 255 directly to the /sys/devices node. jetson_clocks --show and all other software indicators tell me it is indeed set to 255. But in fact, the fan does absolutely nothing (not even twitches).
I bought the fan as part of the same package with the case, which seems to be 3d-printed to fit the Nano exactly, so it would be strange for the fan to be a model that doesn’t work with the Nano. But I have no idea what the model is - ie. is it the 5V or the 12V mentioned in the older thread, or something else entirely. How can I find out?
I’m using an image I downloaded about 2 weeks ago. It was the official stable one at that point. Ubuntu is 18.04, so correlating that with your releases pages, I must have version 4.6.1.
For the power supply I’m currently using the RaspberryPi 5.1V/2.5A (I previously used it with the Rpi so I know it is the “authentic” one).
One thing I noticed - in the images other users post, their fan usually (maybe always?) has 3 wires. Mine has only 2.