The package name field isn't required for use with Urban Airship.
The urban airship platform determines the app to send the notification to based on the 'App Key' in the app, as it will register to different products (in your case, PROD or UAT). That is all that is required to enable Urban Airship to decide which app to send notifications to. As a final note, you do not need to create multiple firebase projects per app variant.
Thank you and regards,