How can I upload .ev3 files to my brick under macOS Catalina
The only way to compile a .ev3 file to a .rbf file is with the "EV3 Lab" software that is not compatible with macOS 10.15 Catalina.

So your options are:


Run Windows or an older version of macOS in a virtual machine, such as VirtualBox
Find someone that can send you the compiled .rbf file, then use a tool such as ev3duder to transfer the program to the EV3.
Write a new program in the new scratch-based programming software.