but you said "I'm trying to connect the monitor like this" so I replied, anyway
Normally you update a firmware on a TV with a Ethernet cable if it don't have one use the USB port. but now you are saying it wasn't possible because you read it online.
Try this way unzip the firmware to desktop and just use your "device manger" and update the driver from there. hope it help you or not
Unfortunately the only way to update the screen is by using the LG software, you can’t download the firmware separately. While connected to the screen with a HDMI or DisplayPort you need to connect an additional data cable, open the LG software, and start the update from there. But the LG software won’t recognise the data cable, no matter what I try.