Recently I realized that even though I was able to add my app's intents in the Shortcuts app, selecting any of the parameters didn't show the popup list of suggestions (the ones declared by DynamicOptionsProvider in the AppIntent subclass) and running it showed an error.
In the image you can see the two suggestions for the working app version ("asdf" and "bla") that would not be there in the non-working version.
I knew that when I had added this functionality, it worked, so I found the app version that caused the App Intents Extension to stop working. Apparently, the problem was that I had removed the Swift files declared in the app extension from my main app's target. Probably when I first added the App Intents Extension I had noticed that adding the extension's source files to the main target made it work, but later thought that it shouldn't be necessary and didn't test if it still worked.
Today I created an empty project with a new App Intents Extension and confirmed that the Shortcuts app was correctly showing the parameter popup suggestions, even without including the extension's source files in the main target. Then during the course of almost an entire day I gradually reduced my original Xcode project to this new sample project to find what else would make the extension work, other than including the extension's source files in the main target.
My very last resource was changing the bundle identifier, which solved the issue. My original project's targets have identifiers like org.domain.OriginalApp and org.domain.OriginalApp.AppIntent, while the sample project's targets have identifiers like org.domain.SampleApp and org.domain.SampleApp.AppIntent.
How could including the App Intents Extension's source files in the main target or changing the bundle identifiers cause the Shortcuts app to correctly show the parameter popup suggestions?