On the receiving end of this controller, there’s probably just a relay shorting 2 wires from the boiler together - like the Honeywell BDR91.
So, you could just replace that by some Shelly switch and wouldn’t have to use the proprietary radio protocol.
On a sidenote: Those room controllers usually “learn” how long it takes to reach the target temperature (as this can be vastly different between summer and winter) and move the starting time accordingly. So they reach the target temperature at the programmed time. At least the more expensive ones do. You’d have to do something similar in your automation if you want that comfort. (Unless HA already has some code for that…)