dev-java/java-config should support python3_9
Can I just double check here: Are you testing these packages and ensuring tests pass with Python 3.9?
Solved with https://gitweb.gentoo.org/repo/gentoo.git/commit/dev-java/java-config/java-config-2.3.1.ebuild?id=5b75eebb6592cbb4b8b2e64d80cbc7ee47f9a3a3