Lightroom Classic 13.5 drag and drop stops working

And this is still happening with the very latest build of Lightroom Classic 14.3.  The problem seems to have gotten worse if anything.  I have taken off various other applications that work on top of Windows, Directory Opus, Media Monkey and none of them produce a demonstrable improvement.  
Is this something that the developers are aware of, care about.  I do sometimes wonder why I'm paying £60/m for these programs.

First troubleshooting steps:

1. Make sure that you are dragging from the center of the thumbnails, not from the grey borders around them. It's a long-time design misfeature that still trips me up about once a year.

2. Restart your computer.

3. Are you trying to drag into a smart collection or a collection set (a folder of collections)?  You can only drag into regular collections and folders, not smart collections or collection sets.

4. If none of this helps, try resetting LR's preferences:
https://www.lightroomqueen.com/articles-page/how-do-i-reset-lightrooms-preferences/

LR sometimes soils its preferences file, and resetting it can fix all sorts of wonky behavior. That article explains how to restore the old preferences if resetting doesn't help.