You actually can deploy thermic actuators (which are usually used as underfloor heating valves) on radiators at ~12 € each, then attach any sort of actuator (Tasmota, ZWave, KNX, RPi hats, whatever is cheapest/most reliable/whatever you feel the most important thing in your environment).
But it means to write the control software yourself.
I did for my underfloor heating and still use battery powered radiator thermostats. It’s really not that bad, it’s more than a year since I had to exchange batteries.
Reliability, well. It’s more dependant on your setup/deployment than on the thermostat hardware.
