Hmm, OK, well that worked, but the database was under /home/astroberry/.local/share/kstars/userdb.sqlite. After I backed up and copied the file over, the HiPS ALL SKY OVERLAY was turned off, and I had to reinstall all the catalogs in DATA under the KSTARS ADD-ON INSTALLER, which is quite a tedious process. I also got this error message when I opened the ADD-ON INSTALLER box that you see below. I had installed these databases when I initially flash Astroberry, because I believe they are really needed, so I couldn't understand why they weren't recognized as already installed. The installer went ahead and installed (or reinstalled) the catalogs anyway, so I'm not sure what that error message pertains to.
What's odd (for me) is that the userdb.sqlite file was exactly the same file size, for the file I backed up, the one I copied, and a backup file that already existed in the folder.
All's well that ends well however. Thanks for your help.