Filter menu entries no longer show why a filter is incompatible
When calling up the Filters -> Alphabetical list some filters will be unavailable due to an incompatible output data type of the currently selected filter in the pipeline browser. In earlier versions of Paraview (before 5.3?) hovering over a greyed-out filter showed why that filter was not compatible (e.g. "Input data must be vtkPolyData"). Since at least 5.3 the greyed-out items are no longer hoverable, so it's become less easy to get some hint as to why a certain filter can't be applied.
Not really a bug, but a case where useful functionality, IMHO, was (inadvertantly?) removed