This is a first attempt to modify Solis inverter settings As SolisMon3, this is based on great work by jmccrohan

This script subscribes to MQTT topics and waits for a message. Once something(HomeAssistant, NodeRed) publishes to the subscribed topic, the script checks the register assigned to topic and reads the register from Solis inverter. If value stored in inverter is not the same as the one in published topic, the new value is sent to inverter.

Modify the values in config.py to match your setup

INVERTER_SERIAL = 1234567890  # WiFi stick serial number
INVERTER_IP = "192.168.1.55"  # IP address of inverter
INVERTER_PORT = 8899          # Port number
MQTT_SERVER = "192.168.1.20"  # IP address of MQTT server
MQTT_PORT = 1883              # Port number of MQTT server
MQTT_USER = ""                # MQTT username, leave blank is no user
MQTT_PASS = ""                # MQTT password
DEBUG = True                  # Enable debugging, helpfull to diagnose problems

Define the topic and matching register in registers.py file. TOPICS_REGS is a dictionary. The key(string) a topic you want to subscribe to, the value is a list with single member(integer) which is register you want to modify. I made value a list as I may add some more stuff in the future.
Here is the example: TOPICS_REGS = {"nodered/solis/minutes": [43004]} The script will subscribe to nodered/solis/minutes on MQTT server and this will be used to modify holding register 43004, which will set inverter clock minutes to desired value.

Run main.py

Docker image is provided.
On your docker host create a folder solismod/config and copy your modified config.py and registers.py files in there.

docker run -it -d --restart unless-stopped --name solismod -v /solismod/config:/solismod/config nosireland/solismod

version: "3.4"

  solismod:
    image: nosireland/solismod:latest
    container_name: solismod
    restart: always
    mem_limit: 32m
    volumes:
      - /docker/solismod/config:/solismod/config
    logging:
      options:
        max-size: 5m

You can use different tools to publish to MQTT. Here is a simple example with NodeRed. I will use nodered/solis/minutes for topic.

1. Change/Add config.py and registers.py values
2. Start the script or docker container
3. In NodeRed add Inject and MQTT out nodes. Connect them together
4. Modify Inject node, give it a name('Minutes) and set payload value to the one you want inverter to be changed to(35)
   
5. Modify MQTT out node. Select your MQTT server, if you have not configured one click on pen and configure it.
   Enter MQTT topic nodered/solis/minutes leave rest blank.
6. Deploy your changes and you should see MQTT out node connected
   
7. Once you click on Inject, the value(35) that you have set will be published to MQTT topic nodered/solis/minutes and since the script is subscribed to that topic, it will try to change the register assigned on the inverter.
   You should see the script showing something similar to below
   

This is a very early draft version and things might not work as expected. Feel free to ask questions.