People who buy Android games on Itch usually understand that they need to download and install the app outside of the Google store, so I don't see that as a problem.
What Itch cares about is that its users get what they paid for. If you offer an Android game and give them an app, you would be complying.
Playing in HTML without installing the app (using a key) would be optional, as long as you are clear, I don't think it would be a problem.