Really not a great experience having your app crash on launch with the first build under Xcode 26 due to longstanding supported functionality that you relied upon being removed without notice.
At a minimum, if this functionality is removed, I would expect Xcode to include a conversion tool that would generate the corresponding code (in Objective-C) from an existing root menu within a storyboard.
Even AI (I asked Google's Gemini, as I'm not yet in a position to install macOS 26 to enable the AI features in Xcode) admits that conversion is a difficult, error-prone task and demurs when asked to do it.
Fixing things that are broken by the WWDC beta with no added value to my app (in fact, only higher development/maintenance cost) is not how I envisioned spending my WWDC week.
Really disappointed by this.