Nicolas Saenz Julienne has contributed a kernel driver for the
Raspberry POE hat fan which is available in 5.13 and newer kernels. I
have 4 RPI4 devices in my home lab running Fedora 34, all powered by
the POE Hat. I was able to get the Hat fan working well with Fedora 34
and the 5.13 kernel. I outline the steps I followed at
for anyone who is interested.
Please note that this process modifies the upstream firmware device
tree file for the RPi4, and that this device tree file is not the same
one Raspberry provides (even though they share the same name).