I don’t think Home Assistant is missing support but I work HVACR.
Are all of your boiler controllers integrated? What’s your boiler setup?
I also have never seen anything usual about any boiler setup.
Do you have a domestic priority taking over control?
Radiant in floor systems can take days to make any noticeable change.
(just one example of the thousands of control possibilities and how it could be a hack job, a variable communicating system, or just a well-installed regular system).
These two topics are using radiators and not in floor but somewhat cover some of the ideas of controlling a boiler:
