Is Google Allo supposed to capable of being the default SMS app? On a Moto G5 Plus with Android 7.0 (Nougat), Google Allo was installed from the Google Play Store.

Going into Settings &gt; Apps &gt; (gear icon) &gt; SMS app the list shown does not include Allo.  Is this universally the case, or is this something 'wrong' with my situation?  Is it correctable?
It's not possible - it's universally the case:


  First off, Allo isn't a Hangouts replacement. You can't set the messaging service as the default SMS client on your phone. It does offer the ability to message a contact that doesn't have Allo installed through Play Services, but that's about it. You can also talk to contacts over SMS, with the message itself routed through Google's servers, but Allo isn't an SMS service by design. In this regard, it has more similarities to WhatsApp than iMessage.



Emphasis added by me.
(source)

Note: It seems that Allo is going to be discontinued.