The test javax/swing/JComboBox/DisabledComboBoxFontTestAuto.java fails on Ubuntu with the following diagnostic:

====================8<--------------------
#section:main
----------messages:(7/372)----------
command: main -Dsun.java2d.uiScale=1 DisabledComboBoxFontTestAuto
reason: User specified action: run main/othervm -Dsun.java2d.uiScale=1 DisabledComboBoxFontTestAuto
started: Thu Jun 15 00:23:39 CEST 2023
Mode: othervm [/othervm specified]
Additional options from @modules: --add-modules java.desktop
finished: Thu Jun 15 00:23:40 CEST 2023
elapsed time (seconds): 0.404
----------configuration:(3/40)----------
Boot Layer
  add modules: java.desktop

----------System.out:(4/78)----------
PASSED
PASSED
PASSED
GTK+ Enabled RGB failure: 117, 117, 117 vs 255, 255, 255
----------System.err:(11/800)----------
java.lang.RuntimeException: FAIL - Enabled and disabled ComboBox does not match in these LAFs: GTK+
at DisabledComboBoxFontTestAuto.main(DisabledComboBoxFontTestAuto.java:178)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
at java.base/java.lang.reflect.Method.invoke(Method.java:580)
at com.sun.javatest.regtest.agent.MainWrapper$MainThread.run(MainWrapper.java:125)
at java.base/java.lang.Thread.run(Thread.java:1583)

JavaTest Message: Test threw exception: java.lang.RuntimeException: FAIL - Enabled and disabled ComboBox does not match in these LAFs: GTK+
JavaTest Message: shutting down test

STATUS:Failed.`main' threw exception: java.lang.RuntimeException: FAIL - Enabled and disabled ComboBox does not match in these LAFs: GTK+
====================8<--------------------

The failure was observed on Ubuntu 18.04, 20.04, 22.04 on both x86-64 and aarch64
It is also reproducible on ArchLinux x86-64

The issue was observed with 21-ea+26-2328, 22-ea+1-7

Reproducibility: ~100%

Steps to reproduce:

$ jtreg -va -testjdk:jdk-22 test/jdk/javax/swing/JComboBox/DisabledComboBoxFontTestAuto.java