Sorry, I have zero experience with the Discourse PWA.
I imagine there is a fundamental flaw in the interaction of a PWA and Discourse as SSO Provider, however: whenever the SSO consumer wants to reauthenticate an already-logged-in-to-discourse user, it’s going to tell the client browser to redirect to the Discourse server, expecting the Discourse server to check the user’s existing cookies and redirect back to the consumer… and expecting all these redirects to happen silently in the browser without the user actually seeing anything except the final page load.
But, the PWA is registered with Android as an entirely separate application which is invoked for certain URL’s/domains, right? When the PWA redirects back to the original browser, how would the original browser know that this new link has anything to do with its original request? And how could Android know that it should only show the PWA to the user if the PWA actually needs input from the user? 