ADDITIONAL SYSTEM INFORMATION :
Tested on JDK 16 Build 21, and the outdated feature flag is still set.

A DESCRIPTION OF THE PROBLEM :
As reported in a comment on JDK-8230869 "This feature started to work properly on 10.15.2 Beta (19C46a), so this fix might be reverted at some point." 10.15.2 was released over almost a year ago and the badge support is still missing in 10.15.2 and newer.

https://hg.openjdk.java.net/jdk/jdk/rev/7dae4286f1cc

apple.laf.JRSUIUtils.java needs an updated isIconBadgeSupported() that detects the minor version of the OS and returns false for 10.15.0 and 10.15.1 but not 10.15.2-7 or 10.16 (or 11.x, in the future, although that's not going to be in this release

Please update to allow users to test the feature and and update the IconBadge. Should be fixed for all supported versions 11 or newer