So everyone is saying the latest firmware removes the Enhanced low power option intentionally?
It seems that you don't understand the post above or you are not reading?
Again there are two august firmware you need to try the other latest firmware with multi-option feature.
What you need to do is download this firmware "Antminer-S9i-xilinx-201907302056-autofreq-user-Update2UBI-NF-sig.tar.gz"
after that flash or update the miner with this firmware through WebGUI.
Then check the miners configuration again. Now you should see the multi-option under miners configuration.