Ok, so I have not messed around with the Ronin-S in a few...

It has a firmware update, but when I download the DJI Assistant 2 - it says it is not compatible with my macOS Catalina

How can I update the firmware?

I have the same issue here

I'm running OS 10.15.6 & had problems connecting the Ronin S with Assistant 2, but after a lot of fussing about with different cables & restarting the Ronin, it eventually worked!Sorry to say that I have no idea what tickeled it into action.

I can't even get the package to install on the computer

Hello, we are sorry for your experiences with the software.
Currently the DJI Assistant 2 does not compatible with the Mac OS Catalina. We suggest you to download the DJI Assistance for Matrice V2.0.13 which has already contained the HoRNDIS Drive and work well with Mac OS Catalina. After this, you can retry install the DJI Assistant 2, it should be work.

We will continue work on the compatibility with Mac OS Catalina and update with you once we fix this issue.

Let me know if you have further questions on that, thank you!