It took a couple of tries and a couple of reboots, but I was able to successfully update the firmware on my H150i, and now I can control everything -- ring lights, fans, fan lights, screen.
(For reference: H150i installed in a 5000T, so two Commanders of various sorts there, plus an LED node, plus an AX1200i. I don't remember exactly how things are arranged, but I have the H150i splitter coming off of one USB header, and an NZXT hub (one of the older ones) coming off of the other splitter.)
Next: In addition to CPU package temperature, could we get the option to use just the straight CPU temperature for display, fan control, etc?