This is version 2. According to my research, the only difference is the supplied bridge which supports HomeKit from Apple in version 3. Version 2 does not yet support HomeKit.
Hello
we only used feller thermostats and i made my room smart. On the tado website there is a configurator to see if the heating system you are using is compatible. in our case, the thermostat is only connected individually in my room and it works perfectly. If there is anything else that is unclear, the customer service can help, and they are very helpful in answering questions. Our heating system manufacturer was available, but the model was not. This was added without further ado.
I hope this answer helps.