I've recently bought a Raspberry Pi 4 Model B, together with its official Case and Case Fan.
After installing Ubuntu Server, noticed that the fan was always running non-stop. The fan has an annoying noise, and it should only run when needed, i.e., when the Pi's temperature rises above a certain threshold.
Contrary to Raspberry OS, where the fan is disabled by default (and can be configured from the UI via Preferences -> Raspberry Pi Configuration -> Performance), Ubuntu Server requires an extra configuration step to be performed from the command line.
After the installation is finished, make sure the system is up-to-date:
sudo apt update
sudo apt full-upgrade
Based on my experiments, this step seems to really be needed, maybe because it installs some Raspberry Pi required drivers/firmware (?).
Finally, edit the file /boot/firmware/config.txt and add the following at the
end of the file:
[all]
dtoverlay=gpio-fan,gpiopin=14,temp=60000
A reboot is needed for changes to take effect.
temp is the temperature at which the fan turns on. By default, on Raspberry OS
it's set to 80º Celsius, but I've decided to set it to 60º Celsius.
To confirm everything is working as expected (the fan is not running non-stop
anymore and turns on and off based on the Pi's temperature) I used
stressberry.