> any sort of pwm control if the fan is plugged in, so it's either full blast or nothing
Got a new network switch that runs somewhat hot (TP-Link) and it's behaving the same way, built-in fan runs either not at all, or at 100% (and noisy at that). Installed OpenWRT on it briefly, before discovering 10Gbe NIC didn't work with OpenWRT, and it had much better fan control. Why is it so hard to just place a basic curve on the fan control based on the hardware temperature? All the sensors and controllers are there apparently, just a software thing...
I have an impression that both noise level and power consumption are not a priority for home network equipment manufactures. After moving to a new house and connecting to another ISP I've got an ISP modem-router which: 1. has a fan and while it's quiet it's not silent 2. consumes around 20 Wt, not much but working 24x7 it would cost around £45/year at current electricity rates.
I think it's technically possible to make a modem which will consume less power and use passive coiling but I don't think they (ISP and device manufacturer) care.