I am not sure if Mitsubishi PAC-US444CN-1 Thermostat Adapter (https://shop.rfwel.com/mitsubishi-pa...ter-interface/) will allow indoor unit SVZ-KP24NA to go below 67°F with the use of a third-party thermostat. I have tried Kumo Cloud Mitsubishi Electric PAC-USWHS002-WF-2 and MHK1.
No, Mitsubishi PAC-US444CN-1 Adapter is just an interface that you would use to connect a 3rd party thermostat for a Mitsubishi Unit. It has no bearing on if the unit is able to go below 67°F, though.
Obtaining the MHK2 thermostat, which is the upgrade from the MHK1, would be able to change the minimum heat setting to go below 67 degrees. This would only work in heat mode.
The MHK2 would have the same type of setup and comes with the receiver that it would connect to.
For other custom HVAC control solutions, feel free to contact our HVAC experts for assistance or learn more about other thermostats on our HVAC Controls website.