I'm using Ubuntu Server 20.04 LTS. The dtparams setting does not work, instead you need a udev rule.

The fan config is in `/sys/class/thermal/cooling_device0/`, if you `cat /sys/class/thermal/cooling_device0/type`, it should be "rpi-poe-fan".

Once you've confirmed that, use this udev rule as an example:

```
SUBSYSTEM=="thermal"
KERNEL=="thermal_zone0"

# If the temp hits 75c, turn on the fan. Turn it off again when it goes back down to 70.
ATTR{trip_point_3_temp}="75000"
ATTR{trip_point_3_hyst}="5000"
#
# If the temp hits 78c, higher RPM.
ATTR{trip_point_2_temp}="78000"
ATTR{trip_point_2_hyst}="2000"
#
# If the temp hits 80c, higher RPM.
ATTR{trip_point_1_temp}="80000"
ATTR{trip_point_1_hyst}="2000"
#
# If the temp hits 81c, highest RPM.
ATTR{trip_point_0_temp}="81000"
ATTR{trip_point_0_hyst}="5000"
```

Place it in `/etc/udev/rules.d/50-rpi-fan.rules`. To apply udev rules, issue `udevadm control --reload-rules && udevadm trigger`