Being open source means you can change everything. The question is how much time you want to spend on this 
I would expect the easiest it to do it through openHAB, create a group of sensors that publish on different MQTT topics (including the internal) and then configure the triggering temperature to start heating when the highest (MAX) sensor value goes below your target temp (the temperature set on the LCD/app) and to stop when even the MIN of the group reaches desired temp…
Richard (rlkoshak) has suggested this approach in the past.
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