Finally got it working on my Asrock X570D4U-2L2T board.
Step by step guide.
Login to your ASRockRack IPMI web ui (BMC)
Go to Settings -> FAN Settings -> FAN Mode
In the lower section "Set Fan Control Mode" set all fans to "Manual" and press the "Save control mode" button
Open a ssh session to your unraid server or use the unraid web terminal
Go to the following directory by entering the command
cd /usr/local/emhttp/plugins/ipmi/scripts
Download the custom ipmi2json file
wget https://raw.githubusercontent.com/lucasteligioridis/IPMI-unRAID/master/source/ipmi/usr/local/emhttp/plugins/ipmi/scripts/ipmi2json
Set the permission for the file
chmod 755 ipmi2json.1
Exchange the original file with the custom one
mv ipmi2json ipmi2json.ori && mv ipmi2json.1 ipmi2json
Download the custom ipmifan file
wget https://raw.githubusercontent.com/lucasteligioridis/IPMI-unRAID/master/source/ipmi/usr/local/emhttp/plugins/ipmi/scripts/ipmifan
Set the permission for the file
chmod 755 ipmifan.1
Exchange the original file with the custom one
mv ipmifan ipmifan.ori && mv ipmifan.1 ipmifan
Login to your unraid web ui
Go to Settings -> IPMI -> Fan Control
Set "Fan Control" to "No" and press the button "APPLY"
Press now the "CONFIGURE" button and wait until its finished
When finished, press the "DONE" button
Configure now your "Fan Settings" which fan should be linked to which temperature sensor, e.g. HDD Temperature
Start the fan control again by setting "Fan Control" to "Yes" and press the "APPLY" button
Enjoy
NOTES
What is missing is to make the files persistent, so with this guide your would need to repeat step 5-11 every time you restart your unraid server and then stop the fan control and start it again to load the activate the changed files
If you do not set in the BMC your fan control mode to manual, the configure script in unraid will not work properly.
Many thanks again to @cakes044 who made effort to get the raw ipmi values for the board.
cheers,
Horfic
