Binding EGLImage to RenderTexture (or setting NativeTexturePtr)

I'm trying to get a Unity Camera to render to an EGLImage with some help from a native plugin. I'm running this on Android with OpenGL ES 3.2, using a native plugin to create ANativeWindowBuffer and an EGLImageKHR from that. Now, I'm trying to figure out how to use glEGLImageTargetTexture2DOES with a RenderTexture.

Texture2D has CreateExternalTexture static method, which is really what I'd like to use, but Camera.targetTexture only accepts a RenderTexture and there does not appear to be a way of creating one out of a native OpenGL texture object.

Creating a RenderTexture in Unity and then calling glEGLImageTargetTexture2DOES on GetNativeTexturePtr() works, but only for a single frame. For some reason, the binding is reset after each frame, so I have to reassociate the texture with my image each time and I'm not really sure what the performance implications of this are. Is there a cleaner way of either creating a RenderTexture out of an existing OpenGL object, or changing Unity's RenderTexture instance so that the changes persist across frames?