The only reason it did work was because you did an upgrade. I was also on the betas. As an experiment, I backed up my Homebrew install and tried one from scratc

The only reason it did work was because you did an upgrade. I was also on the betas. As an experiment, I backed up my Homebrew install and tried one from scratch. Failed badly. Very important things like gnu-readline would not compile. I couldn't even get as far as nvim. Packaging work was already being done under 2.1 to fix what was broken, and Catalina bottles were already appearing. By the time Catalina final came out, it was usable from scratch, but only if you had homebrew installed under /usr/local so you could rely on the aforementioned bottles. I was using an alternative prefix of /opt/homebrew. (I have been for years). When I attempted to continue using that, a few packages for which there were Catalina bottles would not compile, and so could not be installed under /opt/homebrew. I finally gave up, and started from scratch under /usr/local. I REALLY don't like how homebrew insists on /usr/local for stability. The whole "do yourself a favor" mentality speaks to something broken in their packaging methodology. Any package should be able to be compiled under any prefix. And for the most part they can be, except for the exceptions that the core team or package maintainer doesn't care about because "you were warned." I wouldn't mind using /usr/local were it not for the fact that lots of other installers want to put stuff there, and it can cause conflicts. Keeping homebrew in an isolated prefix makes a lot more sense. /usr/local was and remains a poor choice.