When I run a Neo Geo rom from either GnGeo or FB Alpha, I get the “Press Start” text and insert coins. Then, once the game starts I get, for example, Metal Slug ammo info and lives. Also full sound. But no game sprites or background layers. I’m fairly experienced in emulators and ROMs on Mac and Windows machines so I’m aware of the usual, i.e. Bios rom and unzipping it or not. But never on Linux. So this just seems to be a settings problem. Maybe?
Also, CPS2 ROMs work fine in FB Alpha. Does the Pi version not play NG?