Has the automatic thumbnail update feature been removed from Lakka 4.3? Not the “Playlists Thumbnails Updater” under “Online Updater” but when you highlight each game. I can’t find this option anywhere.
Bump 
. Has this feature been removed with 4.3?
I don’t have 4.3 currently installed, as I’m working on the 5.x. Nevertheless 5.x uses currently the same version (git ad89b0c) of RetroArch as 4.3, so it should be the same. When I browse a playlist and select a game, there is an item “Download Thumbnails” - do you mean this?
Maybe you disabled (by accident) the visibility of that item - Settings -> User Interface -> Menu Item Visibility -> Quick Menu -> almost at bottom Show ‘Download Thumbnails’. I do not recall that it would be disabled in default configuration of RetroArch.
There is also a legacy thumbnail-pack downloader, which is disabled by default, that would download zip archive with ALL thumbnails for that system and decompress it in the correct location - see Settings - User Interface - Menu Item Visibility - Show Legacy ‘Thumbnail Updater’. However I would not recommend using this method, as the packs are not updated very often (and maybe they will be dropped completely).
I am not aware of any other ways of downloading thumbnails.
I’ll have to wait until I’m in front of my unit to give the exact location but it may have been under the “update” option. I remember it being at the bottom and saying that when enable, wouldn’t affect system performance or something similar like that. It wasn’t the option when selecting the game but a setting of the main menu.
Having created a live Lakka 4.2 USB, the option “On-Demand Thumbnail Downloads” is located under “Online Update”. This feature is not available under 4.3.
This feature seems to have been moved to Settings, Network under 4.3. This entry can also be found within retroarch.cfg as "network_on_demand_thumbnails = “true”. The RetroArch service needs to be stopped prior to making any changes.