Realm for watchOS: app can not be installed from Testflight


I installed Realm (I have tried from v11.0 to v13.4.2) inside my application that has a watchOS associated app.
All works fine if I run the application from Xcode (v10.2). Instead when I archive and distribute the application in TestFlight then I am able to install successfully the iOS app, but I can’t install the watchOS app in the AppleWatch.

In TestFlight, when I tap on the switch that allows to install the application in the Apple Watch, an error popup saying that the application can not be installed on Apple Watch appears.