It appears the the "Jenkins URL" configuration in the main configuration is not properly over-writable from the configuration as code plugin.

The configuration snippet below is always overwritten at runtime, it seems, with whatever the Kubernetes master Service IP turns out to be. In the case of my local testing of our Jenkins master image, which is not running in Kubernetes, after booting with the configuration below the "Jenkins URL" setting is `http://:`

---
jenkins:
  clouds:
  - kubernetes:
      connectTimeout: 5
      jenkinsUrl: "https://some-external-dns-entry/"