Trying to export an iOS app from a Godot project, I ran into this same Requested but did not find extension point error. I tried nearly all of the solutions found in StackOverflow and in this thread (updating/reinstalling Godot/Xcode/Command Line Tools, selecting Command Line Tools path in Xcode, etc.), and nothing worked for me. Finally, I went through the output of Godot & xcodebuild line-by-line and found this error:
Failed to create provisioning profile. There are no devices registered in your account on the developer website. Select a device run destination to have Xcode register it.
Once I registered my iPhone 11 and Intel MacBook Pro on the Certificates, Identifiers & Profiles screen in my Apple Developer Account, the export completed without errors.