I have Ecobee thermostats that work the same way (cloud or Homekit-only), and I don't have a Homekit hub (or any other Homekit devices). What I did to replace the cloud Ecobee integration is to use Home Assistant on a Raspberry Pi to act as a Homekit controller, and get local control of my Ecobees that way. I then used [RELEASE] Home Assistant Device Bridge (HADB) to bring that locally into my Hubitat hubs.
This gives me all the monitoring I want of the thermostat and some control (that I don't use).
