As an effort to support reusing old Android devices, I'm publishing my package recipe archive.
As of writing, it contains only the library Ulfius 2.6.5 and all of its intermediate dependencies. With this bundle I was able to compile a simple test program and run from ADB shell that creates a REST API from my phone. I was also able to forward this API to my machine through ADB.
I'm targeting ARM CPUs without a dedicated FPU (also called sometimes "soft float" CPUs). In theory, you can recompile these libraries against other versions of NDK as well.