Simple bash script to control AMD Radeon graphics cards fan pwm forked from here. Adjust temp/pwm values and hysteresis/interval in the script as desired. Other adjustments, such as the correct hwmon path might be required as well.
This script was initially meant as an example. Please don't just run it naively and keep in mind that I'm not responsible for failures.
I added simple OpenRC service script. Copy amdgpu-fancontrol script to /usr/bin directory. Copy OpenRC service from service/amdgpu-fancontrol to /etc/init.d directory. Copy config to /etc/amdgpu-fancontrol.cfg. Enable service at startup: rc-update add amdgpu-fancontrol default.