The LG unit is configured as a mono output. To change the configuration to 2.1 stereo you need to connect pin 5 (CFG1) to 3.3V. This is a very fiddly job owing to the size of the IC. I used a very finely ground screwdriver tip to dig under the pin (no heat involved) and managed to lift the pin from its solder pad. I then used a very fine point soldering iron and solder paste to solder a wire from the pin to the +3.3V supply track to the IC (see photo).

Also, you need to lift and re-position 6 of the ferrite beads, 4 for the left and right speakers and 2 for the woofer. The other 2 for the woofer can be left in place. Then connect a jumper wire from the lifted 2 woofer outputs to the now disconnected track where the woofer was connected (see photo).

In my case I did not modify the LG chipboard box as I managed to squeeze 2 x RCA connectors into the space below the power lead input. There are 1.2nF capacitors connected between the + and - outputs of both speaker outputs to the unit 0V.  Shielded cables are connected from the speaker outputs to the tops of the ferrite beads that are now the left and right outputs. (see photo).

I use a Wemos ESP8266 board mounted on a small piece of veroboard to connect the ESP8266 to the relevant pins on the mainboard I2C connector.  In my case I use GPIO12 and GPIO13 (SDA A4, SCL A5) for my interface.

The software (work in progress!!!) can be found here: https://github.com/AcuarioCat/LGSpeakers/tree/master/LGSpeakers

I use Visual Studio 2019 with the Visual Micro extension for programming.

You will need to edit the LgSpeakers.ino file to set your own WiFi SSID and password (I haven't included WPS or any other configuration method) and change the Boards.txt and lgWebServer.cpp (setupOTAUpdate) for your own OTA passwords.

The webserver has ssdp included so the soundbar will appear in the 'Home Automation' section of your Network as LG Sound Bar.