Heatsink fan control software not working

Hi,

I installed Armbian Bookworm Minimal CLI on my Rock 5b and followed the instructions on this post to get the fan to work properly.  Specifically,

git clone https://github.com/lukaszsobala/fan-control-rock5b
cd fan-control-rock5b
make package
sudo dpkg -i fan-control*.deb
sudo systemctl enable fan-control
systemctl start fan-control

However, the software won't start.  When trying to run it manually, I get,

$ sudo /usr/sbin/fan-control 
pwmchip: 0
gpio: 0
pwm-period: 20000
temp-map:
  speed: 0, temp: 20, duty: 8400, duration: 10
  speed: 1, temp: 50, duty: 9600, duration: 2
  speed: 2, temp: 60, duty: 10800, duration: 2
  speed: 3, temp: 70, duty: 16000, duration: 5
Failed to export GPIO, No such file or directory
Failed to export GPIO, No such file or directory
Failed to export GPIO, No such file or directory
Failed to export GPIO, No such file or directory
Failed to export GPIO, No such file or directory
Failed to export GPIO, No such file or directory
Failed to init GPIO

Looking at the source, I think it is trying to access the file

/sys/devices/platform/fd8b0010.pwm/pwm/pwmchip0/pwm0/export

(among others.) That directory exists only so far as

/sys/devices/platform/fd8b0010.pwm/pwm/pwmchip0

and doesn't contain pwm0, let alone pwm0/export.

Listing that directory, I have

$ ls -al
total 0
drwxr-xr-x 3 root root    0 Jul 10 15:21 .
drwxr-xr-x 3 root root    0 Jul 10 15:21 ..
lrwxrwxrwx 1 root root    0 Jul 10 16:48 device -> ../../../fd8b0010.pwm
--w------- 1 root root 4096 Jul 10 15:21 export
-r--r--r-- 1 root root 4096 Jul 10 16:48 npwm
drwxr-xr-x 2 root root    0 Jul 10 16:48 power
lrwxrwxrwx 1 root root    0 Jul 10 15:21 subsystem -> ../../../../../class/pwm
-rw-r--r-- 1 root root 4096 Jul 10 15:21 uevent
--w------- 1 root root 4096 Jul 10 15:21 unexport

I believe this Armbian image doesn't include any firmware, right?  So, could I be missing required firmware? Or, could the needed file be elsewhere?

Thanks for any help,
Richard