This is not true. Which version of GitX are you using? There are a number of different forks, and the one I get from “brew cask install rowanj-gitx” works fine

This is not true. Which version of GitX are you using? There are a number of different forks, and the one I get from “brew cask install rowanj-gitx” works fine on Catalina. It is from 2014, but it’s code-signed and it’s 64-bit. If you are using the older fork from http://gitx.frim.nl/ http://gitx.frim.nl/ then it’s a 32-bit binary from 2009. That version won’t work on current macOS versions, but it will run on my Power Mac.