With Atari800MacX not fully functional with macOS Sierra and with no guarantees that it ever will be, I decided to make a Wine port of Altirra 2.80. It seems to function just fine. The sound works, USB joysticks work, and the frame rate seems fine so I'm going to start to use it.
I tried to attach the file here on AtariAge, but it is over the 50mb limit. I created a DropBox and placed it there: https://www.dropbox....ltirra.zip?dl=0
Hopefully Phaeron is ok with that. If not, please let me know and I will take it down immediately.
I hope this helps my fellow Mac users until a native solution appears.