We just had a furnace replaced and the wire we had going from the thermostat to the furnace was  an old two wire set-up.

In order to have fan control at the thermostat you require four wire set-up, otherwise you need to turn the fan on at the furnace.

I believe for  a remote smart thermostat control you need a 6 wire set-up running from the thermostat to the furnace.

So when upgrading it isn't just your thermostat, it is also the wiring between the thermostat and the furnace.

Here's good info on upgrading:  https://smartthermostatguide.com/thermostat-c-wire-explained/

-G