This is a very simple module that imports ODT files into drupal.
The generated HTML markup is simple, and not all odt features are supported.
This is based on a PHP script that converts ODT files to HTML. So the set of supported ODT features is the one of this script: https://github.com/lovasoa/ophir.php
In drupal, choose Modules > Import from URL
Enter the following url: https://github.com/lovasoa/ophir.php/archive/master.zip
Et voilà.