If your willing to tinker/diy you could use a nodemcu running Tasmota with one of these style of water flow sensors. The data can be brought into HE with Gary's Tasmota Sync drivers.
It outputs pulses which the rate of pulses/minute/second can be counted by Tasmota and then sent to HE for determination.
I think Dan's Hubduino firmware for nodemcu's supports pulse counting but couldn't find a reference. You might want to post on his thread if you want and this idea is of interest.
Here's a couple of examples (not HE specific though).
https://how2electronics.com/iot-water-flow-meter-using-esp8266-water-flow-sensor/
https://iotdesignpro.com/projects/iot-based-water-flow-meter