I have decided to remove Ubuntu which was running RetroArch and Mame and go with Lakka. Of all the Mame cores, which is most likely to work with the majority of roms and display boxart? FBNeo did a good jobs with my Capcom games. Running a manual scan seems to pick up everything but using the rom name and no boxart.
mame-current is a good first try. Use a manual scan but feed it a DAT to get proper names and boxart.
Is it possible to download this DAT file?
Sure. It should work with any DAT (including one for FBN), since it’s just matching zip name to “pretty” name, but one specifically for the correct version of MAME will give you the most reliable matches: https://www.progettosnaps.net/dats/MAME/
Thanks hunterk. That is exactly what I was planning to do. 
@hunterk @Graham:
Does Lakka have the mame-current core installed? If not you have to do it manually.
Progettosnap is sometimes a bit slow to update the dat files.
A more faster way is to download directly from the https://www.mamedev.org/release.html page (the full driver information in XML format works perfectly with RetroArch)
To make the rest work (hiscore, history, gameinit & command) i once wrote a guide which should work with mame-current as well
(you eventually have to adjust the paths according to your system and inatallation [ppa/flat/appimage…]. NB: On linux you don’t need to escape backslashes in he lua file)
You may have problems downloading all boxarts/titles/snaps, since the libretro thumbnail database is quite behind the actual naming convention of mamedev.
You can try this instead (it uses AutoHotkey so you may need a windows environment. Don’t know if it works with wine?)
I had to select the Mame 2015 core instead but seems to work and picked up the flyers. The problem I had was that I couldn’t reconfigure the the keys/buttons (no option to do this). I assume copying the Mame-Current *.so file will work?
The *.so files are the cores.
If you mean copying mame_libretro.so from ubuntu to lakka, yes, this should work.
Alternatively for key configuration in mame2015 you have to use the mame tab menu (press “tab” in-game)
Honestly i’m not a friend of mame2015 (or 2010)
If your system is powerful enough use mame-current or FBNeo.
If not, maybe try mame2003-plus.
Since adding the Mame-Current core, I am now able to configure buttons. Not sure where my other cores are (pre-installed one’s), as this was the only one in the Cores folder (accessible via Samba). Maybe they are not accessible and are only updated on each Lakka release.
Exactly where does that xml file download? I’m looking for and I do not see it.
Forget it, I just saw it, it’s just below.