When running a CloudBees CI (Core) for modern cloud platforms cluster, with release 22.214.171.124, if you create a new managed controller and you choose a Plugin catalog when you are first creating the managed controller, the controller fails to start and emits the error:
An error occurred Default update site connectivity check failed with fatal error: Cannot check connection status of the update site with ID='core-mm-offline'. This update center cannot be resolved. If you see this issue for the custom Jenkins WAR bundle, consider setting the correct value of the hudson.model.UpdateCenter.defaultUpdateSiteId system property (requires Jenkins restart). Otherwise please create a bug in Jenkins JIRA.
Upgrade to CloudBees Core on modern cloud platforms 126.96.36.199 and you will be able to create new managed controllers with plugin catalogs defined at creation time, without issue.
Please reach out to CloudBees support for help with your update by using our Assisted Update process.
If you create the managed controller first, then once it is up and running you can assign a "Plugin catalog" to that running controller without any issues.