Since there is no (yet) working modbus connection to Grundig GHP-MM heat pumps with GR-LC07 controller, the only way to get/set parameters is to tap modbus communication between controller & unit

ghp-mm2mqtt.py is quick & dirty hack to publish eavesdropped communication between unit and controller to MQTT (to be consumed by ie HASS)

basic parameters can be set (modbus 0x06 cmd) via MQTT messages to topic GHP/set/slaveid/addr

4pin SM JST connector: connect your rs485 B to brown and A to red wire (black is GND, orange 12V):

install & run sniffer:

wget https://raw.githubusercontent.com/a1bert01/GHP-MM-sniffer/refs/heads/main/ghp-mm2mqtt.py
#edit to set serial port and mqtt credentials
chmod +x ./ghp-mm2mqtt.py
./ghp-mm2mqtt.py

configure mqtt sensors in HASS