As davexnet said, there is no option or solution for updating or even changing your Web browser. I have looked at this very same thing several times, because in their total disregard and contempt for their paying customers LG have blocked anything that they can not monetarise or anything that might in any way actually enhance your use of their sub par products.
Ohhh ......and they have also started to not support certain web sites and pages that up until now have been available through the web browser, like Youtube, you now have to install the app and thats money in the bank for LG.
Do not waste your time and energy contacting LG about anything, they will just ignore you. My advise to you, get an Android TV box and use that to download any apps you want and any web brower you like and as soon as you get the chance, get rid of your LG TV and buy one that actually does what it is supposed to do.