In a parallel to what I've done in the past for Cardboard, using the simple Android sample for OpenGL ES 2, Rylie Pavlik has converted the teapots demo (from the NDK samples) to OpenXR. And a lot of credit goes to her: The Google sample is a big mess of shared dependencies and support scripts.
A small rant here: Google is really lousy when it comes to learning materials. The samples are always super robust and complicated - and while this reflects on desired skills for a programmer to learn, it also makes for a very daunting learning experience.
AndroidTeapots, was vert well factored and reasonably clear to read. And a miracle here! It's OpenGL ES only! Most examples for OpenXR these days tend to focus on Vulkan (which I'm not afraid of), making for a much more complicated base for a eventual new prototype.
Even with all this quality, there was a fatal issue: the view matrix was being computed upside down! And given that the example uses quaternions (which I could never really wrap my head around), I was really struggling to find a quick fix.
On a whim, the view matrix computation from hello_xr has proven easier to lift and adapt. With a small update to the OpenXR SDK present in the repo, everything was working like charm. With that, a MR was submitted and merged.