sounds like you missed a step. You probably haven't specified the class name of your view controller, which probably doesn't want to be "UIViewController", but some subclass of it that you write. In Xcode, select the View Controller in the Storyboard or .xib file, then in the Identify inspector in the right, enter or select the correct name of your custom view controller class.

If you don't want your users to have to right-click and choose open, you need to notarize the application. In Xcode, choose Archive, then Distribute App. Select the Developer ID option, then Upload. The app should be signed with your company's developer ID, uploaded to Apple, notarized, and returned to you in your archive. Notarization can take a few minutes. You can also do this from a script, see man altool

use your favorite search engine to search for "MFI microcontroller devkit". That should jump-start your efforts.

have you tried using the codesign tool to verify the code signature and notarization status of your app?