OpenJFX has deprecated GTK2 for removal (see https://bugs.openjdk.java.net/browse/JDK-8273089)

For the AWT/Swing usage OL6 / RHEL 6 are still supported until at least June 2024 so it is too early to do that yet but it should be done in the next LTS which is JDK 21 in September 2023

Then remove GTK2 before the following LTS (JDK 25 in Sep 2025) but AFTER June 2024 .. which makes the removal release one of
JDK 23 : Sep 2024
JDK 24 : Mar 2025
JDK 25 : Sep 2025

There should be a CSR and a release note.
Additionally when explicitly specifying jdk.gtk.version=2.2 a message should be printed warning of the deprecation.
Perhaps this should be printed only if jdk.gtk.verbose=true is also specified but we can mull that over later.