A lot of the documentation currently available for learning to create native plugins seems to be from a few years ago, when Corona Enterprise was a thing. It's therefore taken me a fair bit of work to figure out how to get going wtih native development myself, in Android Studio, so I've put together a tutorial documenting the entire process.
The tutorial explains creating a really, really, really basic Java plugin that just reads and writes a string variable and returns it to your Lua app. I'm hoping it stands up as a simple Hello World plugin for new Corona Native developers.
Please be warned that I'm new to this myself and could easily have written something that isn't entirely correct, so if anybody spots an error, do please let me know.