For others that run the Ignition Designer in Linux, do you also have solid black borders around the drop down menus instead of shadows?
This happens for me on 2 different systems - details below.
System 1 details:
Systems 2 details:
Looks like this could just be a Wayland thing.
Here is the same Designer running on "System 2" when running in a GNOME session on Xorg instead of Wayland.
Maybe the sun shines brighter in Wayland?
I get that sort of thing when my NVidia driver's compositor crashes. Not just in the designer, but with many applications. It's one of my cues to reset the compositor. (Missing window shadows and other 3d effects are the others.)
This was also a problem for me on Linux, and when I roped @PGriffith into trying to chase it down with the company that develops the look and feel I don't remember their being a solution... Paul might remember more details.
The thing Kevin's talking about was supposedly worked around in the LaF a long time ago, though a support guy from Jyloo also sent me this JDK bug that's untouched: Loading...
So maybe the workaround they're doing was broken by a JDK update that itself didn't fix the underlying bug? 
Seems a weird regression case, but not totally impossible.
Huh. I wonder if this is the cause of my compositor crashes. I'll have to play closer attention. Not-disruptive to me--I can reset the compositor on the fly.