How to make a completely standalone .apk ?

Ah, gotcha, cool that you have it working with just doing the eject at the end. I started that route, but found I had too many customizations to apply. If you ever end up in a similar boat where you want to keep the ejected bits around, @slorber details some workarounds for continuing to use the Expo client after ejecting here: The hard truth about Managed v. Bare - #5 by slorber