I tried to guess command. As there is no error the command seem to be correct. Yet arguments might be wrong.
There is an option now "clean" or "update".
"clean" recreates from scratch
"update" adds devices only (no removal yet is implemented but planned)
The heating is off here in my office, regular thermostat on the wall says 14C, TRV on the rad agrees at 14.2C while the Shelly says 16.2C - so not very accurate yet.
if the temperature difference is consistent you can probably change the Temperature Calibration +plus x° or minus x°. If the temperature is changing with the temperature of the device (brightness of the screen for example) , this is an other issue....
Does driver shows operating state correctly?
I though of "output" state like a relay state. So linked as a state that is either heating or idle. But without device on hand I just can't validate my assumptions 
ThermostatMode remains on heat constantly.
ThermostatOperatingState goes from idle to heating correctly.
When heat is called for the relay in the device turns on (with very audible click) and the child switch turns on at the same time. And of couse when the device goes to idle they switch off correctly.
That's cool)
One more question: Does thermostat 'Refresh' function works? (to check "Thermostat.GetStatus" command assumption)
I have local change to handle before mentioned unknown notification. So basically a control part remains to fix. I'll try to ask Shelly support for any documentation draft for the thermostat component.
Shelly Wall display 1.2.4 - released! & NEWS - Shelly PLUS 1 (2) - Official Shelly Technical Support Forum (DACH) (shelly-support.eu)
Does device provides some sort of consumption metering in thermostat mode? (I assume it might go trough switch component if child switch is fully live)
I don't seem to get anything logged when I hit Refresh. But hard to really know as the thermostat is logging very frequently anyway.
It will rather log to the parent device. Child device only logs attribute changes. It is basically a simple attribute group proxy.
Nothing logged following refresh to the parent.
I do get one of these messages each time I change target temperature.
dev:93612023-11-11 13:49:02.386warn+55831-09-07T17:42:59+01:00[Europe/Dublin]: Unknown NotifyEvent event [component:Shelly, restart_required:false, cfg_rev:27, id:0, event:config_changed, ts:1699710540179]
dev:93612023-11-11 13:48:39.000warn+55831-09-07T11:28:37+01:00[Europe/Dublin]: Unknown NotifyEvent event [component:Shelly, restart_required:false, cfg_rev:27, id:0, event:config_changed, ts:1699710517717]
Regadring temperature precision. Whell it might be not so bad if it stays consistent. A calibration constant has wery high chance to appear. It is almost usual practice in general.
Moreover I can see Shelly provides ability to use their H&T as an external sensor for their TRV. So there is also a chance to see the same thing with Wall Display thermostat.
But it makes me wonder why they are not trying to implement "virtual thermostat". Technically they have all they need. Using Shelly Plus relay with sensor add-on it is possible to connect multiple temperature probes and even mimic heating floor thermostats (with air and floor sensors).
Offtopic:
This actually drives me to an ides for the bathroom mirror heater. While it is obvious that humidity sensor might be used to control exaust fan, nearly the same condition may be applied to the mirror heater to remove condensate.
Maybe because they want you to sell more hardware?
I like the concept of a display + build in temp sensors and switch to replace an existing thermostat, without battery's.
Yes. I currently have 10 old battery operated Z-Wave Secure SRT321 Room Thermostats (only 1 is Z-Wave Plus) - my plan is that is the Shelly Wall Display is suitable then I will gradually replace the SRT321's.
Thermostat Scheduler sets the target temperature on these devices, but a user can use the dial to adjust the target room temperature until Thermostat Scheduler reset it again. I have an app that sets the TRV's in the room to the thermostat's target temp and controls the boiler as necessary.
So the Wall Display is getting very close now that it has the user settable target temperature dial - I don't want it turning on/off the internal relay (in a bedroom the clicking would be too loud). Ideally, I would like its temperature reading to be accurate, but I have other sensors in every room that I can average the temperature and use that, if I have to.
There will be a version of the Wall Display coming out that does not need a neutral line - that would be very good as I have a good few SRT321's installed where a light switch used to be.
Of course, I need the Wall Display target temperature to be capable of being set by HE - but I'm confident that the excellent work of @dmitry.rozovik will sort that !!!
I do like display also) And I find it interesting to have sort of dashboard device (that can act as a thermostat UI also). Like compact version of what people do with tablets. Pretty much what this module tries to do (except it still needs cloud access to act as a dashboard)
And having ability (as an option) to control external Plus ar Pro modules instead of built-in relay allows to go for even higher loads when nesessary (and such external relay modules might reside inside main electic box which is nice in some cases from perspective of power lines layout).
Moreover one Display unit may actually implement more that one thermostat instance this way. Also might be pretty neat.
Sort of LEGO 
I have plans to make combined climate control. I heave a electrically heated floor, radiator with TRV and AC. And I want to meke them work together taking into account best and cheapest conditions: AC is the most power efficient. But if outside temperature goes way too low system might add or fully switch to other source that is cost effective. And so on.
Having multiple thermostats in one module looks to me like a step in this direction)
I should have done this earlier - but I just turned on Debug Logging on the device.
Tried to set Heating Setpoint to 32C
Got the following logged
dev:93612023-11-12 13:38:30.198debugHTTP Async Response: [id:151, request:[uri:http://192.168.199.27, path:/rpc/Thermostat.Set, requestContentType:application/json, query:[id:0, target_C:32.0]]] ::: [code:-114, message:Method Thermostat.Set failed: Method not found!]
dev:93612023-11-12 13:38:30.117debugHTTP Async query: Thermostat.Set([id:0, target_C:32.0])
dev:93612023-11-12 13:38:30.114infoReceived 'componentSetHeatingSetpoint' request from Shelly Wall Display thermostat 1 (EP1)
This means I didn't guessed the command name.
Hmm.. I will try to go trough all the other components to try once more.
Does thermostat 'Refresh' gives the same error?
Here's what I get from Refresh
dev:93612023-11-12 16:02:28.005debugWS query: {"params":{id:0}, "id":150, "method":"Thermostat.GetStatus", "src":"hub"}
dev:93612023-11-12 16:02:28.001infoReceived 'refresh' request from Shelly Wall Display thermostat 1 (EP1)
Ok
This one might be good.
The wall display indeed looks an attractive device, but I think it is too expensive to use as a thermostat, especially because the sensor does not appear to be working properly (for the time being) + I don't see any major benefits that can justify this high price .
All my switches are made smart with Shelly relays (push buttons). I have a thermostat at eye level in all rooms that functions as a thermostat :-). For this thermostat I use a zigbee thermostat from Aliexspress for the price of less than €30. It is now the second heating season and they work really well. The driver that @kkossev wrote also works very well, it took him a lot of effort, thanks again for that.
Agreed, you can't control other devices with it, but I use my Shelly relay's long and double press for that.
The only disadvantage is that there is no proximity sensor to switch on the display (display is always on). You can dim to 3 levels or switch off the display wit a command, but you can not switch the display via the display. In my case, I dim the thermostat when night falls.
In the end the device only costs €27....
That's a very good price. I've ordered one to play with. They would only allow one to be ordered anyway !!! Dunno why.
Download the Hubitat app
