This is the problem with developing for Apple stuff, it works sometimes, then it doesn't and there is zero help anywhere.
My widgets worked fine on iOS 14 on both the iOS Simulator and a physical device.
On iOS 15 widgets work fine on the iOS Simulator, and I can select a dynamic value. Run it on a physical device and get "No options were provided for this parameter". Why not? They were fine before, so why are they broken now? Where is the Apple documentation that tells us why this has happened? Nowhere. You're left to figure it out for yourself. Which usually means asking on Star Overflow and waiting until someone else has figured it out, while you spend a week trying to fix something you didn't break.
Xcode is pretty poor at giving you hints as to how something can be fixed. Example, accidentally add your IntentHandler.swift file to your main app's target (Target Membership), and you get errors about things not being in scope, but nothing to suggest that the file shouldn't be in that target.
Worst of all, what is the experience that my customers are getting? Are their widgets working properly or not?