Woe is me! In attempting a distro-hop I allowed KDE-neon to use my existing home partition. Although it respected all my regular folders, it removed all existing dot folders (i.e. those hidden folders in Linux which start with a ‘.’)
Although these were theoretically backed up in a folder “dotfiles_backup” I was not able to get my data.db, library.db and darktablerc back. Since I’ve always had darktable create .xmp files, I resolved to import into a fresh db. A little over 40,000 images took less than half an hour to import. So far so good.
I’ve lost my presets, but I can recreate them from edit history of individual images. Had to reinstall scripts and enable certain ones, no biggie. However although the geotagged locations are intact, all my map locations (polygon specified) are lost, sadly.
What is a particular nuisance, however, is the inability to resize modules. Ctrl-mouse wheel used to do that, but now o longer seems to. I cannot find a way to re-enable that in the UI. Am I holding my mouth the wrong way 
?
I pull master from git every now and then and last built on 23 February 2023.
Version: darktable 4.3.0+756~g4f7a1903b