none of the image files have changed, other than the directory change
The change may have happened months ago, and it is only you moving the files that caused Lightroom to take another look at the files and notice that there is a discrepancy.
Overwrite original files. This is bad on so many levels.
I don't see why. Lightroom is saying that it has new metadata that hasn't yet been written to the file, and the file is saying that it is newer than the last metadata written by Lr to that file, so Lr is offering to update the file's metadata.
What are these "many levels?" The image itself won't change, and the metadata Lightroom knows about was at least correct at one point in the past.
Chances are excellent that taking this option will lose no information at all. I regularly take this option when this option presents itself. The only time I let Lightroom load image metadata from disk is when I know for a fact that it has changed externally, such as because I've run ExifTool directly on the file.
the file loses its ratings, labels, keywords, etc.
Only if you never saved the Lightroom metadata to the file, either explicitly with Cmd/Ctrl-S or by enabling the "Automatically write changes into XMP" catalog setting. Otherwise, loading the metadata from the file will restore ratings, labels, keywords, etc. as of the last XMP update time, which was correct at that time at least.
If you're really worried about losing metadata, install ExifTool and run it individually on each file you need to re-sync with Lightroom, redirecting the output to a file:
$ exiftool /path/to/my/photo.jpg > a
Say Cmd/Ctrl-S on that file, then re-run the command above, changing the output file, and
diff the two:
$ exiftool /path/to/my/photo.jpg > b
$ diff a b | less
That will tell you what Lightroom changed. My guess is that nothing substantial will have changed; maybe a last-changed date. If something substantial does change, it's easy to fix it in Lightroom, given the
If you didn't have the "Automatically write changes into XMP" setting enabled, do so. Yes, it slows Lightroom down considerably, but it greatly reduces the chance that you will have this sort of two-way conflict.
This obviously works best on macOS, but you can get the same tools on Windows via either Cygwin or WSL.
The files were moved but imported into a different catalog in their new location
That's a workflow bug. You can entirely avoid the problem by doing the move entirely within Lightroom, so it never loses track of information.
Specifically in this case:
Select the files you want to move to the other catalog
Say "File → Export as Catalog...", selecting the "Export negative files" option, saving the new catalog in the location you want the photos to land.
Switch Lightroom catalogs, then say "File → Import from Another Catalog...", selecting the exported catalog file.
That safely copies the photos to the new location, lets you bring the latest up-to-date metadata over via the temporary catalog file, and then lets you put off deleting the photos from the original location only after you've seen that everything is okay.