I am very interested in using nginx on Android as a backend server, but based on my searches nginx is not officially available for Android phones. There are some unofficial "cross-compilation" ports available (e.g. on Github), but I am hesistant to try those, because they are not officially approved.

I think there's a genuine use case for a backend server on phones. This is targeted by e.g. https://github.com/civetweb/civetweb or https://www.gnu.org/software/libmicrohttpd/, but these don't seem like they come close to nginx in terms of standards or performance.

Since it seems possible to cross-compile nginx for Android, then would it be possible to have someone involved in the project to at least verify a method so that one doesn't need to search and use random 3rd party code?

Nginx also seems available for the Termux environment on Android, but again this is not officially endorsed as a way to run nginx on Android.