Don't bother hooking it up to wifi, just let it run. My parents got one of those with their heat pump install and I never connected it to wifi. The heat pump itself has an exterior temp and humidity sensor it uses to manage defrost cycles. "They" are selling you bunk shit.

Also mechanical or basic programmable thermostats are still very available and whoever told you "you don't have a choice" is lying to your face. If you paid your own money for it, return it.