Smart Thermostat for Electric Baseboard Heaters
A proper transformer-and-relay system is not cobbled together and not makeshift.  It is not particularly complex, and is an excellent and safe way to control electric heaters.  

Relays, readily available in several packaging types, are easily installed at/near the service panel.  This gives a short and simple run of the heavy power wires: breaker to nearby relay straight to the heater.   This also allows both sides of the 240V to be switched, so the heater is fully de-energized when off.   

With a line voltage thermostat, heavy power cables must make a lengthy detour first to the thermostat location, and then to the heater itself. (Which hopefully is not too near the thermostat).  Those thermostats leave one leg of 240V connected at all times. 

Heavy cables and heavy power switching makes heat.  It is better to make that heat at the relay, rather than at the thermostat where it can affect the thermostat's calibration.  You may have heard line voltage thermostats being very sloppy at holding temperature... this is why.  A smart thermostat does nothing to fix this fundamental flaw.  

24V thermostats handle only a tiny switching current, so they do not get warm from the wiring.  

Lastly, line voltage thermostats lock you into only a few products.  Once you go transformer/relay, you can use any modern thermostat, e.g. the Nest.