I have a new LG 43UK6500MLA TV. I noticed in the Settings/General/LG Wireless Keyboard.
It is said that the TV supports a special LG wireless keyboard (probably without USB dongle), so you can type in text fields, because using the remote is slow (mine is simple, not "magic remote" with microphone and speech recognition).
But I recently bought LOGITECH MK345 which is a wireless keyboard AND a mouse with a single USB adapter. I was curious what will happen if I plug it in.
Well - this message appears, and both the keyboard and the mouse work pretty well.
In my opinion they help best in the Web browser!
I guess WebOS is pretty good!