It really really depends on what you have for heating.

Floor heating + heat pump? You don’t need to mess around with target temp much because the principle behind it is thermal mass buildup and maintaining that. You have to tune thermostatic valves on the room level. Then you can have one central thermostat simply slightly change the target temperature with many hours of delay. That doesn’t seem too useful to me to automate.

Do you have radiators? Then you can get zwave or ZigBee valves and tie them together with whatever thermostat that you want in home assistant. Then you can set per room/zone heat depending on whatever sensors you have.

Do you have central forced air heating and air conditioning? Then you have pretty much target temp and on/off control unless you want to put in motorized automatic registers or redesign your entire duct system for per-room duct valves.

Individual heat pumps/airco units with radiator based heating is the most “per room” customizable and probably the most useful to put automations on in Home Assistant.

Ventilation can be useful by monitoring CO2 levels and humidity. Then you can use either the fan units themselves or socket switches to actuate those and put whatever sensors you want wherever it is useful.

I am probably missing some stuff here, but there are only a few HVAC setups that actually benefit from automation, in my opinion. Mainly ventilation, infrared, and non centralized forced air heat pumps.