I’ve been experiencing the same. The only instance links which don’t crash the app, open in a browser from the perspective of that instance, where I’m not logged in. So there’s no “easy” way to subscribe.
I have the original C2, not the Max version. And, it too, has been excellent. It might leave a little to be desired for espresso, but for everything else it’s great.
The AeroPress is my daily driver, simple and delicious.