Any way to change the sensor mode in MTS200 thermostat?

[tuomassalo]

Is your feature request related to a problem? Please describe.

I have a MTS200HK electric underfloor heating thermostat. It has two modes for using the temperature sensors. The official Meross app has Sensor Option menu item, where one can choose between:

1. Air&Floor sensor (default) - the built-in air sensor is used for switching the heating on and off. The floor sensor is used for overheating protection.

2. Floor sensor - the external floor sensor is used for switching the heating on and off. The air sensor is disabled. Overheating protection is disabled.

I have a bathroom with the thermostat outside the bathroom, so my only option is to use the floor sensor mode. I've paired the thermostat with the local-only addon. Everything else works perfectly, so I'm hoping to find a way to set the mode without going back to a Meross cloud based configuration.

Here's the view that shows the device and a diagnostics.json. Note that the thermostat shows the current (air) temperature as the temperature that controls the thermostat.

The history graph shows how the floor temperature rises above the thermostat setting:

Describe the solution you'd like

I hope I could find a way to change the sensor mode without resorting to the cloud based integration. I could investigate this further, but I'm a bit confused about all the components of the local-only setup, and possible places for debugging. Could you give some pointers on where to start looking?

Describe alternatives you've considered

With one thermostat, I also tried the meross_lan integration (with Meross cloud credentials). With that integration, I can see and set the setting:

Here's a dump of sniffed HTTP traffic from HA to the thermostat when I switch on the external sensor mode. I believe the relevant code lives here.

{
    "header": {
        "messageId": "364809d4c2dc478d8f827c71f68ef935",
        "namespace": "Appliance.Control.Thermostat.Sensor",
        "method": "SET",
        "payloadVersion": 1,
        "from": "/app/3875228-REDACTED/subscribe",
        "timestamp": 1728154647,
        "timestampMs": 0,
        "sign": "REDACTED"
    },
    "payload": {
        "sensor": [
            {
                "channel": 0,
                "mode": 1
            }
        ]
    }
}

Finally, here are screenshots showing the setting in the official Meross app.

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