On Android the story is quite simple, spinning up a Chrome Custom Tab is super easy and it shares authentication with Chrome. Only big downside and reason our Android team members avoid using the Android app (and that we are considering killing the Android app) is cause opening a Chrome Tab is slow compared to PWA, so people prefer the PWA.
Being Android though you could possibly automate creating the PWA link and all that Jazz from your app which may be interesting.
On iOS the story is more complex due to Apple bugs.
We have the user API key system @pmusaraj will be working on improving per: Delegated authentication for Discourse Mobile app (which also includes adding documentation)
My recommendation here for you @dfabulich is to hold tight for a month or 2 while we redo our protocol and improve documentation.