I have implemented in app subscription model for IOS & Android successfully and have had it out in production for a while (using NodeJS).
I have to admit, it wasn’t easy at all, but it really should be. I’ve had to google a lot and read over 100+ different sources to make sense of the madness that is App store & Play store subscriptions. My brain hurts. In play store defense, it’s actually quite decent compared to Apple, but there were still some things I had to learn.