This post will interest only Mac users so those of you who worship in another church will probably want to skip it.
I spend almost all of my tube time in either Emacs or Safari but I usually have three applications open. In addition to Emacs and Safari, I have the Messages app running in another workspace.
A Few years ago, I used to joke that I was getting in touch with my inner-teenager whenever I sent a text but these days it’s become mainstream and largely replaced email for a certain type of message. That’s especially true of Messages, which is really more like the old IM chat applications than texting. For a long time, I’ve had F9 mapped to open or switch to Messages but that stopped working when I upgraded to Catalina. That was annoying but not fatal because I could just switch to the workspace where it was the only app running.
I just saw this Daring Fireball post that explains what’s going on. With Catalina, Apple moved non-writable applications from /Applications to /System/Applications and Messages was now living in /System/Applications. Once I remapped F9 to open /System/Applications/Messages instead of /Applications/Messages, the F9 hotkey started working again.
Of course, it’s not only Messages that is affected. If you’re having a problem accessing an application after upgrading to Catalina, you should probably investigate if it got moved.