I needed to add min and max values for the HomeKit temperature items. (As I noted, my sensors were limited to 38 degrees max.) This doesn’t seem like it should be necessary if I already set the HomeKit global setting to Fahrenheit. OpenHAB should know this and adjust accordingly without the need to do anything else. That said, what’s the purpose of these limits anyway?
More details here: (Homekit temperature sensor won't go below 10°C - #16 by dirkdirk)