I have finally gotten MATLAB 2019b to work on my mac with os 10.14.6.
Initially, I could not even get MATLAB to run in Safe Boot Mode. However, after a clean uninstall (including deleting Mathworks folder out of "Application Support" folder, I was able to get it running.
There were four possible sources of conflict: Goolge Drive Stream, OneDrive, Spectacle and Echo Desktop auto-loader (loads when Echo pen connected to USB).
I turned all these off and opened MATLAB and it worked.
I turned off the automatic load of Echo Desktop and turned it back on. MATLAB still working
I also have a piece of software called Spectacle, which sizes windows with keystrokes. I turned that off and have since turned it back on and am still running MATLAB successfully.
I have not started up Google Drive Stream or OneDrive yet. I'm just so happy to have MATLAB working, I don't want to tempt fate. When I turn these back on, I'll post back my results.
I hope this helps someone else struggling with this issue too.
Regards and good luck,