macOS style in ParaView 5.6.1 has changed
The style for ParaView 5.6.0 on macOS:
The style for ParaView 5.6.1 on macOS:
This is either another manifestation of the reoccurrence of the style bug on Windows, or an intentional change was made, as was discussed a while back on the old ParaView developers mailing list.
The update to build against Qt 5.12 may be related.