Using Django as backend for android and linux arm64 applications

I am looking to build a new app. My app needs to run on the Snapdragon HDK that runs android and on Jetson Xavier NX which has a Linux OS running on arm64, I would like to know if I can use Django as server-side with Gunicorn. I will need to call Java and C++ functions from their libraries.

The client side will be react.

Thank you in advance

If you have Python available on your target system, and it’s a large enough environment to run it and everything else you need, then sure, you can do this.
I’ve got a system with Django running under uwsgi and nginx on a Raspberry Pi - works great for what it does.
I’m not sure about calling Java libraries though, unless those libraries expose an external API. Java runs in its own process under the JVM (or, in the case of Android, Dalvik I believe). It’s not like you’re running in the same process and can just call a Java method.

Lets assume I am running my app on an android device and I need to call a Java method that will utilise the device hardware (access camera, use GPU’s etc.) Can I access my java library that will be in the same folder as my src and call it with my python code? This is important because the snapdragon SDK is written in Java.

No. Java code is not a “native” library - it runs within the context of a JVM.
(Well, technically it’s not a hard no - you could write a shim in Java to expose the functionality of that library through an external process, but it’s not a trivial process and it’s not like you can just import that library into your Python code.)