Select "Start" with the remote control if you get a "TV Software Upgrade" prompt.Wait for the upgrade to finish and for the TV to restart itself.With the S905 and S906 chipsets the good thing is that basically every box with the same amount of memory and same Wi Fi chip will be compatible for a firmware donation.Big downside of this way is that you get a box branded for some other manufacturer and that the remote might not work at all.You can update your LG TV firmware by navigating to the LG support site, downloading the firmware to a USB drive and installing it on your TV from the USB drive.If you have a network-enabled TV, you can choose to update your firmware automatically when updates become available.Navigate to the LG website (see link in Resources).
Over time things can get slow or after some "tuning" certain parts not longer respond as the should.
Click "Download This File," navigate to the USB drive folder and click "Save" to save the firmware file on the USB drive. Double-click the LG_DTV folder to open it and press "Ctrl-V" to paste the files into the folder.
Double-click the firmware file you downloaded to display the contents of the archive. Insert the USB drive into the USB port on your LG TV.
It also seems I am one of the lucky guy who already had a quite recent firmware installed - from July 2016.
Considering their release strategy and time stamping procedure the firmware was created sometime Feb- March 2016.