One interesting observation... Disk Utility in Catalina has changed. Previously, in Mojave (10.14.6) and earlier OSes, if you wanted to run First Aid on the startup/home volume, while the OS was running, it would give you a warning that the OS would slow down, and that applications may not run during the process, then leave the background and all applications intact, visible as the check runs.
Catalina takes on a classic, Mac OS 9 approach to its First Aid process, harkening back to the days of the Disk First Aid application. Once it asks you to confirm you want it to run First Aid on the startup/home volume, it hides the desktop and applications behind a blank, blurred background while it runs the disk verify/repair process. Mac OS 9 Disk First Aid did almost exactly the same thing; if you just wanted to verify the volume, it would leave all applications and the background intact, but if you wanted to repair the volume, it'd hide/close all running applications behind a blank background and run the process. All desktop icons would be hidden, as well. Same as Catalina.
I found it interesting. Definitely a "little thing" in the grand scheme of things, granted, but still interesting to see.
