Jenkins core has a dependency to org.connectbot.jbcrypt:jbcrypt:jar:1.0.0 which I believe was originally from Bintray/JCenter. JCenter was shut down some years ago and that dependency can now be found in the Jenkins project's "orphans" repo (https://repo.jenkins-ci.org/artifactory/orphans/org/connectbot/jbcrypt/jbcrypt/1.0.0/jbcrypt-1.0.0.jar).

Would it make sense to try to replace this with version 1.0.1 or 1.0.2 available at the Central Repository? That artifact has a small groupId change (org.connectbot). That would building Jenkins easier as a dependency to the orphans repo is removed. (There could maybe be other artifacts retrieved from there, but this is the one I found trying to build.)

I'd be happy to provide a PR for this if so.