Here’s how I got SQL Developer working:
The one that caused the problem is the
"Oracle Corporation" - "Java" /Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home and you’ll need to remove it.
sudo rm -rf "/Library/Internet Plug-Ins/JavaAppletPlugin.plugin/"
If you run SQL Developer now it should work. I’m not sure about the side effects of removing this Java applet plugin. If I find it to be critical to other things I’ll be sure to update this post.