Get Tado thermostat relay status

I have 3 wired Tado thermostats.
I would like to know the status of the relay (open / closed) and plot this on a historical graph to know how the thermostats are activated over time.
Is it possible?

I cannot find the Tado entity that trigger the information on the status (open / closed = heat request / NOT heat request)

You might approach this differently.
I am not familiar with the TADO thermostat, but most thermostats (when supported in HA) show the SET temperature and the Actual temperature

Both Entities can be read.
You could make an automation that looks at those 2 values.

If the value “Room temperature” is 0.3 degrees below the “Set temperature” the relay status is “On”
If the value “Room temperature” is 0.1 degress above the “Set temperature” the relay status is “Off”

In this way you don’t need to “see” the actual status of the relay

Another approach:
there are a large number of DEVANTECH devices that support Input (closed circuit) detection
Most of the DEVANTECH devices can be read using a script.
By looking at the input (once every second) you “know” when the relay is closed or open.

Of course when that relay is in use to control your Central Heating, you can not use that relay.
You will need another (extra) relay that is switched ON /Off by the Thermostat relay, but does nota have just one switch, but 2 switches.
The first one actually controls your heating. The 2nd switch is the one you are using to detect if the relay is switched on (closed)

The last solution is more expensive (you will need a Devantech module and optionally a relay) but in this way you have the Actual status of the Thermostat relay

Good luck

About the first approach (the simplest). I noticed that TADO vole thermostats activate the relay a few tenths of a degree before reaching the set temperature. This is because they do not use an ON / OFF setting but follow a PID.
I cannot understand how this product does not allow simple on / off verification. It is not possible even from APP.