Hey, yes, you are correct that lr-mame2003 and lr-mame2010 use the same retroarch.cfg.
I went to /opt/retropie/configs/mame-libretro/retroarch.cfg and added “rgui_config_directory = home/pi/RetroPie/roms/arcade/”. I then went into startrek.zip.cfg and added “video_smoothing on”.
I can see my custom cfg when setting launch options before launching into the game.
Neither step had any effect in lr-mame2010.
I should mention that the game runs in the correct orientation by default in lr-mame2003. When I load the game in lr-mame2003, it rotates the game 90 degrees counterclockwise, as per my custom cfg (the same result I want in lr-mame2010). The reason I’m not running it in lr-mame2003 all the tie is that lr-mame2003 doesn’t emulate the sound at all.
I have no idea why this is happening, save that lr-mame2010 might not be set up to read the custom cfg…