Does Catalina synch and backup devices running iOS 12? I've got one of the first generation iPad Airs and it will only update to iOS 12.4.2.  I'm trying to back it up and synch it using my iMac on which I've installed Catalina (10.15). The iPad shows in the sidebar of Finder but when I click on it, after a minute of waiting I get a message saying "The selected device could not be found."  I have no problem backing up and synching my iPhone which is running 13.1.2 and I've had no problems backing up and synching this iPad in the past. Does anyone know if the new method works with devices running iOS 12?
I would suggest you try this: 

https://www.catalinaosx.com/macos-catalina-continuity-issues-device-timed-out/