The following situation is common: you have 2 windows opened (may be windows Java FX application, may be JavaFX and any other application). One window is active (target) and you want to drag there some data from JavaFX window (source). You click on source and start to drag.
Drag and drop does not work in this case on linux.
Work on Windows though.
Not a regression

Can be tested with any kind of drag and drop. Can be drag and drop within one window or between different windows. In attachment there is simplest Drag & Drop project from Samples. To use it you should make another application active before starting drag (say, File Manager).

Netbeans project in attachment. Can be launched with java -jar <jar from dist folder>