Yes, we know, we started to work on an AMP compatible set of form, but they require a strict integration with amp plugin since the AMP form feature must be loaded and the form need to make ajax posts and few other little things.
We hope to be able to release a specific extension for AMP (or we can all hope AMP will die :-).
Still no news about an AMP version? It’s really needed! I’d like to add a subscription form to the AMP version of my site, and it turns out there is no way to do this with the Newsletter plugin.