I have done a clean install of macOS Catalina and installed the latest Java SE 13 and JavaGUI, and Eclipse.
SAPGUI works fine on it's own. Eclipse also works, I can do any ADT-Native stuff. But when Eclipse tries to open a SAPGUI tab I get an error
The system reqirements are not met. Could not find: javafx.properties in: /Library/Java/JavaVirtualMachines/jdk-13.0.2.jdk/Contents/Home/lib Your Java Virtual Machine seems not to support JavaFX, required to run the SAP GUI for Java 7.50 rev 8.
This is the same issue as already described here: https://answers.sap.com/questions/787056/javafx-11-and-eclipse-issue.html
But when I apply the same solution Eclipse doesn't start. Running it from a terminal I can see the reason:
% ./eclipse Error occurred during initialization of boot layer java.lang.LayerInstantiationException: Package jdk.internal.jimage.decompressor in both module jrt.fs and module java.base %
The path I added was the javafx in the SAPGUI installation, because it is the only one on my entire system:
% find /System/Volumes/Data -name javafx.properties 2> /dev/null /System/Volumes/Data/Applications/SAP Clients/SAPGUI 7.50rev8/SAPGUI 7.50rev8.app/Contents/Resources/jre/Contents/Home/lib/javafx.properties %