For other System 5 MC owners that are still on Sierra or High Sierra, Mojave works fine for us. We tested with Pro-Tools 2019.10.0 along with eucon 3.6.1.
We will wait until Pro-tools is approved for Catalina before testing it but It's great to see that the System 5 MC still works well in Mojave. Worst case scenario, we will stay in Mojave forever.
