I had seen a reference to a script called amdgpu-fancontrol in the arch wiki about fan controls, when I was looking to set the fan speed for my rx550.
The referenced script (modified since I started using it) is at https://github.com/grmat/amdgpu-fancontrol
It's a simple shell script, similar to the cpu fan control script from lm-sensors.
I've been using it for a week now, no problems, the temp has remained stable, with the fan at 0 rpm.

