According to the manual, if you dial in heat on the climate control and the coolant temp is cooler than 57 degrees F (14 C), the ICE will start. So if you don't want the ICE to run, dial the temp on the climate down below ambient temp, so that the climate system doesn't think you are trying to heat the cabin.
In most conditions, the AC won't start automatically if you just have the fan on. So an easy way to maintain this in summer weather is to just turn the climate temp all the way down to min, turn the climate system Off, and then turn the fan on.
The condition where the AC might start automatically, without giving you an indicator light, is when you put the climate system in the defog configuration. So don't use that one if you don't want the AC to start. And if you occasionally forget these rules and the AC runs for a few minutes every month, that's actually good for your AC system, so don't fret the few pennies lost. But don't drive around all summer in defog mode (I usually notice when I've made this mistake because the air coming out the vent is cooler than it should be for no AC running).
2018 Niro PHEV Gravity Blue