Smart Thermostat with dumb add ons

I was looking at thermostats, but in my house there are 4 thermostats, 3 in bedrooms and one in main living area. We have baseboard heat (radiator, not electric)

My question is this, do I need 4 smart thermostats, or is there one smart thermostat that can have add on “dumb” thermostats that only talk back via zwave or other?
I have not seen anything like I describe, but maybe my google-fu is weak today.

Thanks again for any help.

You need 4. I am I the same boat and spent 1k on Nest thermostats over the past few years.