Since doing this could result in a bricked set, we always follow LG's instructions to the letter.
It's also not something you get from a non-LG site (like here!) since the instruction can change and this site would be out of date. No one would update the instruction here and that's a danger to all.
This is why you get referred back to LG for updates.
I have a 2016 model and am having difficulty in tracking down the process for loading down the latest firmware. There are multiple sites that appear to offer this (general) info for LG sets but nothing specific to this UK model.
Would appreciate the help/
Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic