Atari 800 Core?

Has there been any development on an Atari 800 core? This was the video game / computer system I grew up with, and I’m very eager to see if I can get it running in RetroArch. I have a Kodi addon called IARL (Internet Archive ROM Launcher) and it lists an Atari 800 library, but I don’t know what core RetroArch has that would support it. I asked the IARL developer and he suggested using MAME, since they’ve joined forces with MESS and now have both capabilities. However, I can’t make it work. Has anybody had any experience getting this to work at all?

I’m on a Raspberry Pi 3, running LibreELEC 7.0.2 and RetroArch 1.3.6