I have TRVs in my home but as i dont have a dedicated wall dashboard the only way i can manually control them if needed is through the app. Is there an external thermostat which i can put in each room and to show the current temp, the target temp and to have buttons to adjust the target temp? I assume if there a small touchscreen LCD which can display a single HA card will work too.
There are wall thermometers made for this use case.
You did not specify which technologies you would prefer or if it should be battery or mains powered.
The technology does not have to be the same as the TRVs, but if you have a technology in use already then it might be a good idea to see options for that one first, before starting up with another one.