= Removal of old backend system support Support for the old backend system was removed from multiple plugins: app,events, proxy, search, techdocs, user-settings, auth-backend, catalog-backend, and others. End-user plugins that are not yet migrated to the new backend system may require updates. Imports using /alpha must also be updated. = Frontend discovery now respects discovery.endpoints The frontend now uses the discovery.endpoints configuration, which may alter how plugin requests are routed. Existing setups relying on backend base URL defaults may be impacted. = Rejection of branch names with slashes in GitHub catalog module Branches with slashes (e.g., feature/foo) are now invalid and will be rejected during catalog ingestion. = Default GitHub branch in scaffolder changed to main Scaffolder templates publishing to GitHub now default to main, the defaultBranch input can be used to override. = CodeOwnersProcessor removed from default catalog processors The CodeOwnersProcessor is no longer included by default, it must now be registered manually via catalogProcessingExtensionPoint. = Deprecation of React 17 React 17 is deprecated. The Backstage CLI will warn if it is still in use. Upgrade to React 18 is recommended.