Thx, I am now at least able to statically control the fan using. Following Guide on how to customize you pwm fan curve
root@rock-5-itx:~# echo user_space > /sys/class/thermal/thermal_zone0/policy
root@rock-5-itx:~# echo 90 > /sys/devices/platform/pwm-fan/hwmon/hwmon9/pwm1
However, the overlay PWM cooling map trips in for the rock 5 itx seems to be completely missing in https://github.com/armbian/linux-rockchip/blob/rk-6.1-rkr3/arch/arm64/boot/dts/rockchip/rk3588-rock-5-itx.dts#L971-L987 and I am not sure how to add it manually.