Lost Edits when Transferring Photos

Folders using the date convention are only created on import, not when you drag and drop folders. This has never been different in the past.

I'm not sure what you did with that new folder, but if images are created with a '-2' behind the name, then that is something the MacOS Finder did in order not to overwrite existing images. It created duplicates and obviously those duplicates will not have edits in Lightroom. The originals should still be in Lightroom and still have their edits, however. You say that you dragged the images over in Lightroom, but it sounds a lot like you actually did something else, like importing again. Dragging images should never create duplicates. If the folder you try to drag them to already contains copies, then you should get an error dialog.

Importing images again can indeed create duplicates if you copy them during import to a folder that already contains copies of the images, but Lightroom isn't aware of these copies.

Then, when I'd set up a new folder in the external hard drive with the correct date and dragged the relevant photos over there, again within Lightroom, new photo labels were created (e.g. AAB_2758-2) and the edits were lost!

What are labels? There are no structures in Lightroom Classic that are called labels.

Why do you say the edits were lost, what do you see, where did you look? Please be specific and detailed. Did you look in the History Panel? What does the history panel say? Show us a screen capture of the history panel of one of these photos so we can see (use the "Insert Photos" icon, do not attach files)

I can locate the original photos in Finder, but the edits have been deleted there too.

Edits should not be seen in the Finder. They are only visible in Lightroom Classic.